Buckingham Fire and Rescue Service is urging people to take extra care during the hot weather.
Firefighters have been called to a number of fires in the open parks and countryside since June.
One appliance and crew from Bletchley attended a fire in the open at 11:50am on Main Road, Drayton Parslow.
Two days later, in a suspected arson attack, firefighters were called to a field fire in Mill Lane, Great Brickhill, at 12:44pm.
An appliance and crew from Bletchley and one from Broughton attended and firefighters used a main jet.
Officers are asking people to follow The Countryside Code when they are out in parks and open fields.
The code applies to all parts of the countryside and is designed to help everyone respect, protect and enjoy the countryside.
Community safety manager Richard Priest said: “Every year, fire destroys thousands of acres of the UK’s countryside and wildlife habitats.
“Some fires are started deliberately, but most are due to carelessness.
“Obviously you should be careful at all times of the year, but dry ground in the summer means there is an added risk of a fire starting.”