GCRI · Climate and Hazards
Heat and drought
Extreme heat and drought are slow to start and costly to end. Heat harms people, crops, livestock and infrastructure within days; drought builds over months as rainfall deficits pass into soils, rivers and aquifers. This page sets out how heat and drought develop, how they are measured with standard indices, and what evidence serves the services and ministries that prepare for them.
Heat and drought on the record.
Heat and drought: how the risk develops.
Compound heat and hydrologic stress. The dossier below sets out how the risk develops, what is measured, where the data come from, how it is modelled and who decides.
Heat domes and dry soils
Persistent high pressure brings clear skies and subsiding air. Dry soils return less energy as evaporation and more as heat, so drought and heat reinforce each other.
Humidity sets the human limit
The body cools by sweating, which fails as humidity rises. Wet-bulb and heat-stress indices combine temperature, humidity, wind and radiation to describe the load on people.
Drought propagates through the water cycle
A rainfall deficit becomes soil moisture drought, then streamflow and groundwater drought, each with a longer lag. Recovery follows the same order, so aquifers can stay low long after rains return.
Impacts cross sectors
Heat raises electricity demand while reducing thermal plant cooling and line capacity. Drought cuts hydropower, river transport and irrigation at once, and the losses compound.
Water now worldwide.
Root-zone soil moisture, rain and daytime surface heat across the world, from NASA GIBS. Each layer carries its own date.
The interactive map needs JavaScript; the layer list and sources are below.
Layers 3
Water now, for this page
About this layer
- Evidence
- Modelled
- Source
- SMAP Level 4 (NASA NSIDC DAAC)
- Provider
- NASA NSIDC DAAC
- Licence
- NASA open data
- Vintage
- daily; Model with satellite data assimilated
- Newest at build
- 2026-10-11
- Resolution
- about 2 km grid
- Uncertainty
- Model with satellite data assimilated. Satellite or model raster as the provider publishes it. Clouds, swath gaps and retrieval error leave gaps and noise; values are indicators, not measurements at a place.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Estimated
- Source
- GPM IMERG (NASA GES DISC)
- Provider
- NASA GES DISC
- Licence
- NASA open data
- Vintage
- daily; Satellite estimate, near real time
- Newest at build
- 2026-10-12
- Resolution
- about 2 km grid
- Uncertainty
- Satellite estimate, near real time. Satellite or model raster as the provider publishes it. Clouds, swath gaps and retrieval error leave gaps and noise; values are indicators, not measurements at a place.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed (persistent cloud still leaves gaps)
- Source
- VIIRS NOAA-20 Level 3, 8-day (NASA LANCE)
- Provider
- NASA LANCE
- Licence
- NASA open data
- Vintage
- 8-day; Satellite 8-day composite; persistent cloud still leaves gaps
- Newest at build
- 2026-09-14
- Resolution
- about 1 km grid
- Uncertainty
- Satellite skin temperature of the ground over the 8 days ending on the date shown, a heat exposure indicator; not air temperature, heat index or a heat warning.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed
- Source
- VIIRS NOAA-20 corrected reflectance (NASA LANCE)
- Provider
- NASA LANCE
- Licence
- NASA open data
- Vintage
- daily; Satellite image
- Newest at build
- 2026-10-14
- Resolution
- about 250 m grid
- Uncertainty
- Satellite image. Satellite or model raster as the provider publishes it. Clouds, swath gaps and retrieval error leave gaps and noise; values are indicators, not measurements at a place.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed (clouds leave gaps)
- Source
- VIIRS Global Flood Product (NASA LANCE)
- Provider
- NASA LANCE
- Licence
- NASA open data
- Vintage
- daily; Satellite detection; clouds leave gaps
- Newest at build
- 2026-10-14
- Resolution
- about 250 m grid
- Uncertainty
- Satellite detection; clouds leave gaps. Satellite or model raster as the provider publishes it. Clouds, swath gaps and retrieval error leave gaps and noise; values are indicators, not measurements at a place.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Modelled (latest year GIBS publishes)
- Source
- MODIS Terra and Aqua land cover (MCD12Q1) (NASA LP DAAC)
- Provider
- NASA LP DAAC
- Licence
- NASA open data
- Vintage
- yearly; Satellite classification; latest year GIBS publishes
- Newest at build
- 2024-01-01
- Resolution
- about 500 m grid
- Uncertainty
- Satellite land cover classes for the year shown, including croplands; a classification with known errors, not a farm register.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
Keyboard, with the map focused
Hold Ctrl or ⌘ and scroll to zoom
Latest available
NASA GIBS / EOSDIS · ASTER GDEM (METI, NASA) · Blue Marble (NASA) · © OpenStreetMap contributors (ODbL) · Natural Earth
Loading the latest NASA imagery.
Drag to move. Ctrl or ⌘ and scroll, pinch or the buttons to zoom; hover for the values under the pointer; reset returns to the region.
Water now, framed on the world.Satellite and model products as NASA publishes them, each with its own date. They are indicators, not assessments of any place.
Data: NASA GIBS · ASTER GDEM · Blue Marble · © OpenStreetMap contributors · Natural Earth · NASA EONET · NASA SMAP · NASA JPL OPERA DIST-ALERTSources and licences
- We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- SMAP Level 4 soil moisture and snow mass, NASA Global Modeling and Assimilation Office; distributed by the NASA National Snow and Ice Data Center DAAC; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- GPM IMERG precipitation, NASA Precipitation Processing System; distributed by the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- VIIRS near-real-time products (flood, land surface temperature, snow cover, corrected reflectance), NASA LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- MODIS land products (vegetation indices, gross primary production, land cover), NASA LP DAAC and LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- ASTER GDEM is a product of METI and NASA (ASTER Global Digital Elevation Model V003, NASA LP DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). Cite as: NASA/METI/AIST/Japan Spacesystems and U.S./Japan ASTER Science Team (2019). ASTER Global Digital Elevation Model V003. doi:10.5067/ASTER/ASTGTM.003. NASA open data
- Made with Natural Earth. Free vector and raster map data @ naturalearthdata.com. Public domain
- © OpenStreetMap contributors (ODbL), via NASA GIBS (coastlines, boundaries, roads and place names). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). ODbL
- Blue Marble, NASA Earth Observatory; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- Context on the globe and flat map: coastlines, boundaries, roads and place names from NASA GIBS reference layers (OpenStreetMap data, ODbL, © OpenStreetMap contributors); Blue Marble imagery as an optional base; 3D terrain and the elevation read-out from the ASTER GDEM elevation colour index (5 m to 200 m classes, exaggerated for legibility). Boundaries are drawn as published and imply no position on any territory.
- Live events: NASA Earth Observatory Natural Event Tracker (EONET); events are indicative and keep their original source links.
- Live: NASA EONET Events are indicative, not authority warnings.
- Observed (EO): NASA SMAP. We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS).
- Observed (EO): NASA JPL OPERA DIST-ALERT (contains modified Copernicus Sentinel data 2026). We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS).
- NASA GIBS: We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS).
- River discharge forecast, 30 days with range (GloFAS via Open-Meteo): Contains modified Copernicus Emergency Management Service information 2026; not a flood warning.
- Past year, daily temperature (ERA5 via Open-Meteo): Contains modified Copernicus Climate Change Service information 2026.
- Past year, daily temperature and sunshine (NASA POWER): These data were obtained from the NASA Langley Research Center (LaRC) POWER Project funded through the NASA Earth Science/Applied Science Program..
- Weather data by Open-Meteo.com (https://open-meteo.com/), licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).
- Optional layers (14 sources in the layer list: live, forecast, observed and context) print their provider credit on the map and here when switched on; forecasts are model output and derived indices are estimates.
Layers and dates
- Root-zone soil moisture, 0 to 100 cm: SMAP Level 4, NASA NSIDC DAAC · 11 Oct 2026
- Precipitation rate, daily mean: GPM IMERG, NASA GES DISC · 12 Oct 2026
- Land surface temperature, day, 8-day composite: VIIRS NOAA-20 Level 3, 8-day, NASA LANCE · 14 Sep 2026
- True colour: VIIRS NOAA-20 corrected reflectance, NASA LANCE · 13 Oct 2026
- Flood water, 3-day composite: VIIRS Global Flood Product, NASA LANCE · 14 Oct 2026
- Land cover type (IGBP), yearly: MODIS Terra and Aqua land cover (MCD12Q1), NASA LP DAAC · 2024
Heat and drought reach every domain within one season.
- HealthCouplingHeat raises mortality, especially among older people and outdoor workers.What to watchExcess mortality during heat episodes
- EnergyCouplingHeat raises cooling demand while reducing plant and line capacity.What to watchPeak demand on hot evenings
- FoodCouplingHeat and dry spells at flowering cut yields sharply.What to watchHeat stress days in crop stages
Heat and drought analyses are designed for the Country Systems Risk and Resilience series. Drought indices follow WMO guidance (SPI, WMO-No. 1090, 2012); attribution of heat events, the strongest area of attribution science, is reported with method and confidence.
- Local heat-health outcome data, aggregated.
- Drought impact records from farms and utilities.
Multi-hazard outlook.
The screen a team would use to follow this subject: its measures, states and decisions. Names are examples and values are illustrative.
What is measured, and how well.
Each indicator carries its unit, its cadence, the kind of source behind it and the evidence label a value would carry. No values are shown: a programme supplies them under its own authority.
| Indicator | Unit | Cadence | Source type | Label |
|---|---|---|---|---|
| Standardized Precipitation Index | standard deviations at a stated accumulation period | monthly | Gridded precipitation | OBSERVED |
| Standardized Precipitation Evapotranspiration Index | standard deviations at a stated accumulation period | monthly | Gridded climate data | ESTIMATED |
| Soil moisture anomaly | percentile against reference period | daily to monthly | Satellite retrievals and land models | MODELLED |
| Heatwave days | count of days above a local threshold | seasonal | Station and reanalysis temperature | OBSERVED |
| Wet-bulb globe temperature | degrees Celsius | hourly | Station data or reanalysis | ESTIMATED |
| Vegetation condition | anomaly of a vegetation index | dekadal | Satellite vegetation indices | OBSERVED |
| Streamflow percentile | percentile of flow for the day of year | daily | River gauging networks | OBSERVED |
Model heat and drought as a system. Run the cascade.
Assembled from the Nexus Standards area profile Climate risk standards: the hazards it names, the systems and sectors that carry the loss, the controls that dampen it and the data that observe it. Choose the components, pick an initiating hazard and step through the cascade. The Map view places the run on an example geography with open data. Every coupling weight is a stated assumption you can change. A teaching model, not a forecast, an assessment or a certification. To model a place of your own choosing, open the full System Builder.
Hazards
- Sea-level rise
- Coastal flood (set off downstream)
- Storm surge (set off downstream)
- High-tide flooding (set off downstream)
- Coastal erosion (set off downstream)
- Saltwater intrusion (set off downstream)
- Estuary flood (set off downstream)
- Coastal habitat squeeze (set off downstream)
- Wetland loss (set off downstream)
- Mangrove loss (set off downstream)
- Groundwater flood (set off downstream)
- Climate-driven migration and relocation (set off downstream)
- Mass displacement (set off downstream)
Systems and couplings
Controls
NS-0Constitution and principlesNS-1The UNI and the artefact catalogue (grammar v0.2: domain, sector, region and environment segments)NS-3Risk record UNIs (grammar, legacy crosswalk, allocation authority)NS-3bDataset and product metadata profile (STAC, DCAT, PROV-O)NS-9Contextual UNIs (deployments, instances, programme instances)NS-11Verification and monitoring (evidence, attestations, zero-trust conformance observation)NS-14Conformance and crosswalk to external standardsNRS-H65Hazard family: Planetary boundary transgressions (NHS-1 planet.boundary)NRS-H62Hazard family: Compound and multi-hazard events (NHS-1 sys.compound)NRS-H71Hazard family: Deep-time and cosmic catastrophes (NHS-1 planet.deep-time)NRS-H79Hazard family: Mental health crises (NHS-1 health.mental)NRS-H75Hazard family: Climate-sensitive illness (NHS-1 health.climate-sensitive)NRS-H7Hazard family: Large-scale circulation anomalies (NHS-1 atmo.climate-mode)
Observation
- ERA5 reanalysis (Copernicus Climate Data Store) (listed for reference)
- CMIP6 climate projections (Copernicus Climate Data Store) (listed for reference)
- NGFS Scenario Explorer (listed for reference)
- INFORM Risk Index (listed for reference)
- Number of deaths, missing persons and directly affected persons attributed to disasters per 100,000 population
- Total greenhouse gas emissions per year
- Direct economic loss attributed to disasters in relation to global GDP
Example geography
- Pacific Island states: 150 hexagonal cells
- Night lights tonight, outages (VIIRS Day/Night Band), NASA GIBS
- Surface water through cloud, 30 m (OPERA DSWx-S1 radar), NASA GIBS
- Rain rate, last half hour (IMERG), NASA GIBS
- Vegetation disturbance alerts, 30 m (OPERA DIST-ALERT), NASA GIBS
Where the evidence comes from.
Named public datasets and institutional records, each with its licence class. Sources by agreement are used only under their terms and never republished.
| Source | What it gives | Licence class |
|---|---|---|
| Copernicus European and Global Drought Observatories (JRC) | Drought indicators including precipitation, soil moisture and vegetation | Free, Copernicus and JRC terms |
| SPEIbase (CSIC) | Global gridded SPEI at multiple time scales | Open, licence to check |
| ERA5-Land (Copernicus Climate Change Service) | Land surface temperature, soil moisture and evaporation fields | Free and open with attribution, Copernicus licence (to check current terms) |
| NASA MODIS and VIIRS vegetation products | Vegetation indices and land surface temperature | Open, NASA data policy |
| Global Runoff Data Centre (WMO, BfG) | River discharge records from national services | Free for non-commercial use, GRDC terms (to check) |
| Global Drought Information System (NOAA and partners) | Drought monitors and outlooks | Public, terms per source |
Coupled risk, applied response.
The sectors heatwave touches and how strongly they depend on each other: what a study has to observe and model together.
Choose a context
Sectors · HeatwaveStress
Pillars · HeatwaveKPI
In this contextDependence or handoff, heavier is strongerOutside this context
Programme yearAll phases
Context
Heatwave
Cooling demand peaks the grid while rivers warm; heat stress fills hospitals and wilts crops.
W · E · I · F · H · B
Risk
- Sectors
- 4 of 6
- Relations
- 6 of 15
- Coupling
- 0.43 share of total
Hover a corner, a line or a row to trace it across both sides.
Route
Applied to heatwave
L · F · U · S · R · A
Response
- Pillars
- 4 of 6
- Handoffs
- 10 of 18
- Loops
- 5 closed
Expected value
- What is at stake
- –no published benchmark
- Return on resilience
- –no published benchmark
- Avoided loss
- 1,190deaths avoided a yearHess et al., J. Environ. Public Health, 2018
Hover a pillar, a line or a row to read how it is applied.
A: a teaching cascade (shock 0.6, gain 0.35, four rounds) over teaching values for a typical city-region, not measurements. B: illustrative applications and the KPI each pillar answers for; values are published benchmarks, cited, not forecasts. Open events: NASA EONET, live.
Who decides, and what the evidence serves.
Climate and Hazards prepares evidence. The decisions below are taken by the authorities named, under their own rules, and never by the platform.
| Who decides | The question | Evidence this page serves |
|---|---|---|
| National meteorological and hydrological services | When to declare drought conditions or issue heat warnings | Standard indices against thresholds; propagation status |
| Ministries of health and labour | Which heat-health thresholds trigger action plans and work restrictions | Heat-stress climatologies; heatwave day records |
| Water and agriculture ministries | How to allocate water and plan irrigation under drought | Soil moisture and streamflow percentiles; drought outlooks |
| Energy regulators and grid operators | How to plan for heat-driven demand and drought-reduced supply | Joint heat and drought evidence by season |
Outputs this topic produces
- Drought monitoring dashboards built on standard indices, with labels
- Heat-stress climatologies for cities and workplaces
- Drought propagation analyses from rainfall to groundwater
- Hazard evidence notes for sector ministries
How heat and drought is modelled, measured and tested.
The model, its assumptions, its data and its uncertainty, in the form a scientist or engineer would check. Structures follow published methods. The values drawn are illustrative, not findings.
Uncertainty bands
How far the outlook for heat and drought could spread, shown as ranges rather than a single line.
- Central estimate
- median of the ensemble
- Ranges
- likely and very likely, in IPCC calibrated language
- Ensemble
- members, scenarios and initial conditions stated
- Read with
- the sensitivity of the result to each input
What experts ask.
The questions concern intensity, duration and coincidence.
- How have the frequency, intensity and duration of heatwaves changed, including night-time heat?
- Which type of drought matters for a given decision: meteorological, agricultural, hydrological or groundwater?
- How do soil moisture and temperature feed back on each other?
- How likely are heat and drought to occur together, and over large areas at once?
- How do humidity and heat combine to affect the human body?
Mechanisms and drivers.
Heat extremes are increasing as the climate warms, and the increase in extremes is among the clearest signals in the observational record. Persistent high-pressure systems trap warm air; dry soils then reduce evaporative cooling, so more of the sun’s energy heats the air, which in turn dries soils further. This land-atmosphere feedback is one reason heat and drought so often coincide.
Drought develops over weeks to years and propagates through the water cycle: a rainfall deficit dries soils, then reduces river flow, then depletes reservoirs and groundwater. Higher temperatures increase evaporative demand, so droughts can intensify even where rainfall does not change. Humid heat is particularly dangerous because it limits the body’s ability to cool through sweating.
How it is studied, and where the methods stop.
| Method or data | What it shows | Limits |
|---|---|---|
| Temperature and heat-stress indices | Heat intensity, duration and humid-heat exposure | Indices differ, and thresholds for harm vary by population |
| Standardised drought indices | Deficits in precipitation and evaporative balance | Each index captures a different type of drought |
| Soil moisture and vegetation from satellites | Agricultural drought over large areas | Measures mainly the surface; needs ground validation |
| Hydrological models | River flow, reservoir and groundwater stress | Water management and abstraction are hard to represent |
| Multivariate and extreme value statistics | Joint likelihood of heat and drought | Short records limit confidence in rare combinations |
How it is studied, and what the methods cannot say.
- 01Climate and atmospheric scienceDetection and attribution of change · Extreme event attribution · Process-based model evaluationApplied here
- 02Extreme value theory and tail riskReturn level estimation · Non-stationary extremes · Regional frequency analysisApplied here
- 03Hydrology and water scienceCatchment flood modelling · Drought propagation · Flood frequency with changing climateApplied here
- 04Earth observation and remote sensingFlood extent mapping · Vegetation and drought monitoring · Active fire and burned areaApplied here
- 05Forecasting and time-series analysisEnsemble forecast interpretation · Seasonal outlook use · Forecast verificationApplied here
Where this page’s references lead.
The bodies and documents this page is read against. Status and editions change; each link goes to the issuing body.
Questions and answers.
What is the Standardized Precipitation Index?
What is the difference between meteorological and hydrological drought?
What is wet-bulb globe temperature?
Why do warm nights matter?
Can it be in drought while it is raining?
Does the platform declare droughts?
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