Between April 1 and July 31, there were 3,433 reported arsons across West Yorkshire, compared to 2,946 during the comparable period the previous year.
The figures were discussed at a meeting of the West Yorkshire Fire Authority yesterday.
Of the incidents, 564 were classed as primary arsons – involving a house, business or property – and 2,871 were classed as secondary arsons – involving fires in the open or waste being set on fire.
Deputy Chief Fire Officer Dave Walton told members the year had been “exceptional” for arson incidents. He added: “This year’s figures are significant, and in part are undoubtedly due to the hot weather. In April and May the arson levels were actually lower than previous years, but then the sun came out in June and July. In July the numbers more than doubled.”
Coun Caroline Anderson (Con, Adel and Wharfedale) asked how fire crews could determine if a grass fire was arson without evidence.
Mr Walton replied: “They are classed as deliberate when crews determine that is the most probable cause. Also we are often dealing with one fire and the people who started it are up the road starting another.”
One of the most high-profile arson incidents in that period was at Jewson’s builder’s yard in Hunslet in July. At the meeting Mr Walton revealed that an arrest had been made in that investigation.
During the same discussion, members were told that in the four-month period there had been 21 attacks on firefighters.
When asked why there seemed to be so few arrests over attacks on firefighters, Mr Walton said it was often difficult securing evidence, adding: “A lot of the time we are talking about something being thrown at staff in the dark, from some distance away.”