Mittagong firefighters responded to the three fires in two days on Monday and Tuesday.
Crews attended a tree fire at Leopold Lane, Mittagong at about 3.15pm on Tuesday afternoon.
The source of the fire is believed to be a nearby pile of wood that became alight.
Captain Gerry Conway said the fire was not being treated as suspicious.
Meanwhile on September 11 at about 8.57am, Mittagong fire brigade and Bowral Fire and Rescue responded to a fire on Hawkins Drive, Mittagong.
Mittagong crews were first to arrive and found a fire in one of the main buildings at the pool.
Bowral Captain John Arnot said the building was adjacent to a chemical storeroom, and the fire was being treated as suspicious.
Also on September 11, Mittagong crews responded to a car fire in Owen Street, Welby at about 5pm.
Captain Gerry Conway said the fire was deliberately lit, and residents saw several young people seen leaving the area.
The incident is currently under police investigation.
The bushfire danger period for the Wingecarribee will commence in a fortnight.
Anyone who wishes to light a fire during the period must obtain a permit from the fire control centre.
Homeowners are advised to prepare for the upcoming fire season, with warmer than average temperatures and below average rainfall forecast.