The most serious was at The Oval in Harrogate, where three fire engines and an aerial ladder platform were sent to tackle a blaze in a disused three storey building at around 6.15pm.
A North Yorkshire Fire Service spokesman said: "The fire was due to rubbish being lit within the property. Three youths were escorted from the building by fire crews and given a precautionary check by ambulance."
Crews from Harrogate and Knaresborough used two hose reel jets and four breathing apparatus sets while putting out the fire.
It followed an earlier call to the skate part in Harrogate's Valley Gardens after rubbish was set alight.
Crews were called there at around 5.20pm but found the fire was already out when they arrived.
Meanwhile, engines from Kirbymoorside and Helmsley were sent to a fire at a derelict property in Swineherd Lane, Kirkbymoorside, at around 7.45pm.
A fire had begun in the stairwell of the empty building and is believed to have been started by children.
Crews used a thermal imaging camera before putting out the fire using a hose reel.