More than 40 firefighters have been tackling a large crop fire in a field near Dartford in north Kent.
Kent Fire and Rescue Service said the fire at New Road, Horton Kirby started at about 1300 BST on Monday.
The service said the warm weather had dried out vegetation, fields and woodland and crews had seen an increase in the number of call outs.
Horton Kirby crew manager Kevin Porter urged people to make sure they disposed of their cigarettes safely.
He added: "As the conditions are very dry, these fires have the potential to spread very quickly, posing a threat to people, wildlife and buildings.
"We want to encourage people to take care and think about what they're doing. For example, people should dispose of cigarettes safety, and drivers should refrain from discarding cigarettes through car windows while driving along as this, combined with dry grass verges, can easily start a fire.
He added: "At this time of year another problem is young people deliberately setting fires.
"This activity is destructive and dangerous and those who cause them are putting themselves, and others, at serious risk, as well as diverting valuable firefighting resources from other incidents."