This article is part of The Purple Report September 2026 | Disaster Forecasting and Predictions and focuses on compound heat, drought and wildfire risk.
Heat, drought and wildfire are often described as separate disasters.
In reality they frequently form a sequence.
Heat raises evaporation and physiological stress. Drought dries soils, rivers and vegetation. Dry fuels make ignition easier and fire spread faster. Fire removes vegetation and alters soils. The next intense rain can then create erosion, flash flooding or debris flows over burned ground.
A compound climate disaster is often a moving state, not one event.
Quick Read
The September baseline tracks seven compound heat/drought/fire systems:
- Iberia and southwest France — HIGH-CONCERN
- Greece–Türkiye / eastern Mediterranean — ELEVATED
- California wildfire–atmospheric-river belt — WATCH
- Southeast Australia — WATCH
- Amazon–Pantanal — WATCH
- Greater Horn of Africa — WATCH
- Sahel and West African urban flood–heat belt — WATCH
These are climate-conditioned watches. They can strengthen or weaken seasonally. None is a prediction that a specific wildfire, drought or heatwave will occur at an exact place and date.
Why September 2026 Begins With an Elevated Climate Background
The World Meteorological Organization’s August–October 2026 seasonal outlook says a strong El Niño is developing and expected to intensify, alongside widespread above-normal temperature probabilities and a positive Indian Ocean Dipole.
The WMO decadal update for 2026–2035 also expects global temperatures to remain at or near record levels in the coming years.
Neither statement tells us where the next wildfire will ignite.
They change the background state against which local rainfall, fuels, water supply, heat exposure and fire weather operate.
WMO — Global Seasonal Climate Update Aug–Oct 2026
WMO — Global Annual to Decadal Climate Update 2026–2035
Iberia and Southwest France: Why September Starts HIGH-CONCERN
Western Europe enters the September baseline after an exceptionally hot and dry June–July 2026.
Copernicus reports that western Europe experienced its hottest June–July period in its 1979–2026 record and that prolonged dryness favoured extreme wildfire activity. July soil moisture and river flow were exceptionally low across large parts of the dry region.
This follows a 2025 European climate year in which WMO/Copernicus reported record wildfire burned area, major heatwaves and widespread below-average river flow.
The September HIGH-CONCERN label therefore reflects recent heat + dryness + fuel/fire conditions + water stress.
It should fall when rainfall, soil moisture, fire weather and official conditions improve.
Copernicus — July 2026 heat, dryness and wildfire conditions
WMO/Copernicus — European State of the Climate 2025
Eastern Mediterranean: Heat, Fire and the Rain That Comes After
Greece, Türkiye and neighbouring eastern Mediterranean systems combine summer heat, dry fuels, tourism exposure, steep terrain and highly variable rainfall.
Wildfire is not the only endpoint.
Burned hillslopes can lose vegetation and change infiltration. Later intense rainfall can produce rapid runoff, erosion and debris movement.
The forecast therefore carries state across seasons:
heat/drought → fire → burned landscape → intense rain → flood/debris risk
This is a memory problem. The autumn rainfall forecast needs to know what the summer fire did to the catchment.
California: Fire and Atmospheric River Share the Same Mountains
California’s multi-hazard structure is a useful example of why related hazards should not be studied in isolation.
Drought and heat can create severe wildfire conditions.
After a fire, an atmospheric river can deliver intense rainfall to a watershed that has lost vegetation and developed water-repellent soils.
The resulting debris flow may threaten roads and homes that survived the original fire.
This creates two forecast clocks:
- fire-weather/fuel conditions before ignition;
- post-fire debris-flow conditions when heavy rain later arrives.
A system that clears the wildfire alert and forgets the burn scar has thrown away useful state.
Southeast Australia: Longer Fire Seasons and Heavier Rain Can Coexist
Australia demonstrates why climate change is not simply “everything gets drier”.
CSIRO and the Bureau of Meteorology report an increase in extreme heat, longer fire seasons and more intense heavy rainfall events.
Southern Australia has experienced declining cool-season rainfall in important regions while heavy rainfall extremes become more intense.
This means the same landscape can spend longer drying and still experience intense flood-producing rain.
CSIRO/Bureau of Meteorology — State of the Climate
Amazon–Pantanal: Drought, Smoke and Hydrological Reversal
The Amazon and Pantanal are tracked as a compound ecosystem–human system rather than a single wildfire zone.
Drought can reduce river transport, stress ecosystems, increase fire susceptibility and affect agriculture.
Smoke becomes a health and aviation problem.
Then the water cycle can reverse and produce flooding.
WMO’s Latin America and Caribbean climate assessment describes an increasingly extreme water cycle, record heat, wildfire and glacier pressures across the region.
WMO — State of the Climate in Latin America and the Caribbean 2025
Greater Horn of Africa: Drought and Flood Are Not Opposites in the Forecast
A region can move from drought stress into damaging flood without “returning to normal” in between.
Drought can weaken livelihoods, livestock health, food security and household buffers.
Then intense rain can produce flooding over a population whose recovery capacity is already depleted.
WMO reports that floods were the most frequently reported hazard in Africa in 2025 while dangerous heat and drought also affected large populations.
People and communities can carry the effects of one hazard into the next.
WMO — State of the Climate in Africa 2025
Sahel and West African Cities: Heat Plus Drainage
The Sahel and rapidly growing West African cities combine several apparently contradictory pressures:
- extreme heat;
- water stress;
- intense convective rainfall;
- fast urban growth;
- large areas of informal housing;
- drainage constraints;
- limited early-warning coverage in some countries.
A city can therefore experience heat catastrophe and urban flood risk in the same season.
The forecast should not label one “wet” and one “dry” as though those categories cannot coexist.
The Compound-Risk Factors
| Layer | Useful evidence |
|---|---|
| Heat loading | temperature anomaly, wet-bulb/heat-index conditions, night-time heat, duration |
| Drought | precipitation deficit, soil moisture, river/reservoir state, groundwater |
| Fire weather | temperature, humidity, wind, fuel moisture, lightning, drought indices |
| Exposure | population, workers, farms, forests, power lines, tourism, wildlife |
| Health vulnerability | age, cooling access, outdoor work, air quality, healthcare capacity |
| Cascade | power demand, water shortage, smoke, transport, crop loss, post-fire debris flow |
| Recovery | firebreaks, evacuation, cooling, water storage, grid redundancy, burn-scar monitoring |
What Would Raise the Watch?
- persistent extreme temperature forecast;
- very low soil/fuel moisture;
- strong dry winds;
- exceptionally low river or reservoir levels;
- large active fires near dense populations or critical infrastructure;
- smoke exposure affecting large populations;
- heavy-rain forecast over recent burn scars;
- power/water systems already stressed before the weather peak.
What Would Lower It?
- meaningful rainfall that restores soil/fuel moisture;
- cooler temperatures and weaker fire weather;
- recovery of river/reservoir state;
- containment of active fire;
- restored grid and water margins;
- burned catchments stabilised before major rainfall;
- new evidence reducing the assumed seasonal loading.
September 2026 Compound-Risk Ledger
| System | State | Main reason |
|---|---|---|
| Iberia / southwest France | HIGH-CONCERN | record June–July heat/dryness + extreme 2026 wildfire conditions |
| Greece–Türkiye / eastern Mediterranean | ELEVATED | heat/drought/fire + post-fire rainfall cascade |
| California | WATCH | fire–atmospheric-river compound structure |
| Southeast Australia | WATCH | longer fire weather + intensifying heavy rain |
| Amazon–Pantanal | WATCH | drought/fire/smoke + hydrological reversal |
| Greater Horn of Africa | WATCH | drought/flood/food/heat compound vulnerability |
| Sahel / West African urban belt | WATCH | heat + intense rainfall + fast urban exposure |
The Ten-Year Question
The forecast does not ask whether each of these places will burn or flood every year.
It asks whether the underlying climate and land-system dynamics are changing the frequency, intensity or recovery burden enough that preparedness should change over the decade.
The most dangerous climate hotspot may be the place where one season quietly removes the resilience needed for the next season.
Primary and High-Authority Sources
- WMO — Global Seasonal Climate Update Aug–Oct 2026
- WMO — Global Annual to Decadal Climate Update 2026–2035
- WMO/Copernicus — European State of the Climate 2025
- Copernicus — July 2026 European heat and wildfire conditions
- CSIRO/Bureau of Meteorology — State of the Climate
- WMO — Latin America and Caribbean 2025
- WMO — State of the Climate in Africa 2025