Dorset Fire and Rescue Service say that arsonists are believed to have started a fire which destroyed heathland on Ham Common in Poole yesterday.
Large fires at Canford Heath and Studland are also thought to be the result of individuals deliberately starting fires.
The service is calling on people to recognise the serious danger posed by the wild fires to people and property.
More top news
Saturday evening's pollen forecast
The latest weekend weather for the east of the region
The latest weekend weather for the west of the region