Firefighters were called to tackle two grass fires last night, as the hot weather and tinderbox condition continues.
A grass verge off Rigby Road in central Blackpool went up in flames overnight, as smoke poured over the top of the Yeadon Way bridge, while a passerby was also forced to use sand from a nearby road sign to put out flames on Lytham Green.
Chris Hay, a sports coach, wrote on Twitter: "Drove past two boys around 14 laughing, starting a fire. Disgraceful behaviour from the two teenage boys."
A spokesman for Lytham Fire Station said it was "shocking behaviour," and added: "We have spent 14 hours at Winter Hill again today and can't be in two places at once.
"Resources are stretched and this is not only illegal but life-threatening."
Road police officers were called to the fire off Rigby Road, which they said started as the result of "careless behaviour."
The longest heatwave for decades has left grass incredibly dry, and a tiny spark can cause a fierce blaze, as seen on Lytham Green and the nature reserve on the dunes at St Annes last weekend.
The moorland blaze at Winter Hill, near Chorley, continues to burn and has been described as the "biggest natural disaster for decades."
Some 15 fire engines are there this morning, and will be joined by firefighters from London later.
"Please take care when you are out today, and keep away from the exclusion zone," Lancashire Fire and Rescue Service warned.