Firefighters are dealing with up to five field or grassland blazes a day during the heatwave – many deliberately started.
On Tuesday afternoon alone, crews in Sheffield and Rotherham spent hours dealing with five large fires on fields, grassland, wood chippings or grass. All but one had been started deliberately.
Now South Yorkshire Fire & Rescue is urging people to lower the risk of fires.
A spokesman said: “The good weather has left areas of the county tinder dry and the risk of a fire getting out of control is really high.
“We’re asking the public to help us in two ways.
“First, if you visit the countryside, take your rubbish with you, as glass and plastic left lying around can easily start a fire.
“Dispose of cigarettes carefully and position barbecues somewhere safe, like a stone surface well away from buildings, shrubs and trees.
“Second, if you spot someone starting fires deliberately, contact police.
“The maximum sentence for arson is life in prison and even a small fire can quickly spread, potentially putting lives at risk.”
On Tuesday, fires included an accidental field blaze at Underhill Farm in Birley Carr where Tankersley firefighters spent three hours bringing it under control, while grassland was deliberately set ablaze on Wainwright Avenue, Richmond.
Another arson attack at allotments on Penrith Road, Longley, saw wood chippings deliberately set on fire.
In Rotherham, railway sleepers and grass banking at Armer Street, Masbrough, was set ablaze, as were football pitches on Sandy Lane, Thurcroft.
On Wednesday, scrubland was set on fire on Edmunds Road, Worsbrough Dale. Barnsley and woodland off Kestrel Avenue, Thorpe Hesley, Rotherham.