Rain going missing
What Is a Drought?
A drought is not just no rain — it is much less rain than a place is built around.
-
Step 1 of 5
Drought is relative, not absolute.
A desert getting its usual 5 cm of rain is fine. A rainforest getting 5 cm would be a catastrophe. Drought means much less than normal for that place.
-
Step 2 of 5
Rain-bearing weather simply stops arriving.
A stubborn area of high pressure can park over a region for weeks, pushing air downward. Sinking air does not form clouds, so no rain falls.
-
Step 3 of 5
The ground dries from the top down.
Soil moisture goes first, then streams, then reservoirs, then deep groundwater. Each stage takes longer to empty — and much longer to refill.
-
Step 4 of 5
Dry ground makes itself drier.
Plants normally release water into the air, which helps make rain. Once they wilt, that moisture stops, and the drought reinforces itself.
-
Step 5 of 5
Recovery needs steady rain, not a downpour.
Which is why hosepipe bans often outlast the weather that caused them. Hard rain on baked ground runs straight off. Gentle rain over days soaks in. One dramatic storm can end a heatwave without ending a drought.
Long droughts can lower the ground itself, as emptied aquifers compact and the land above sinks permanently.
The short version
A drought is a long shortfall against normal rainfall, and dry ground makes the shortfall worse.
Try it yourself
Pour water on dry compacted soil and on damp soil. The dry one repels it — which is why droughts are hard to break.