The basin of Grafham Water in Cambridgeshire is visible, where water is receding due to the continued dry weatherThe fourth heatwave of the year is set to peak on Wednesday with temperatures of up to 35C, as experts warn wildfires could be “exceptionally severe”. The alert is in place from Tuesday to Thursday, and the agency warned that rising temperatures may increase health risks, particularly for vulnerable groups. Temperatures are expected to peak as high as 35C across south-east England on Wednesday. Phil Garrigan, chairman of the NFCC, said: “More than 200 wildfires in just 12 days shows how quickly the risk can escalate when hot, dry conditions take hold. Fire chiefs said people should report any signs of fire immediately by calling 999 and asking for the fire and rescue service.