It comes after an official drought was declared across more than half of England and all of Wales.
On Wednesday the Environment Agency declared a "flash drought" across more than half of England, where water is being used up much faster than nature can replenish it.
Wisley in Surrey has seen a 44 consecutive days without recording any rainfall as of 30 July.
Scotland does not declare drought but monitors "water scarcity". Some parts of eastern Scotland are in the most extreme category of "significant scarcity", according to the Scottish Environment Protection Agency.
The drought conditions have led to significant impacts, including low river flow and early harvests. More than 20 million people are already under hosepipe bans in a bid to conserve water.
The hot weather and lack of rainfall has led to tinder-dry conditions, which have exacerbated the risk of wildfires spreading.
A major incident was declared in Suffolk on Wednesday as firefighters tackled a wildfire "the size of 200 football pitches".
In Scotland, a wildfire in the Cairngorms burned for two weeks, destroying 10 sq miles (25 sq km) of moorland.
Northern Ireland is not currently in drought.
