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.
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Rain becoming more persistent overnight. Rain and cloud slow to clear tomorrow but becoming dry by the afternoon. Some brightness later
Rain becoming more persistent overnight. The rain gradually clearing tomorrow morning then sunny spells for the afternoon, feeling cooler
Becoming brighter with warm sunny spells developing this afternoon but also the risk of heavy showers