Today's weather will be perfect for families heading to South Bank's Streets Beach. Photo: Glenn Hunt
The mercury is set to reach 32 degrees in Brisbane on Wednesday, about six degrees above the September average.
Ipswich, just west of Brisbane, will be even hotter, hitting 33 degrees.
"There will be quite a contrast between western suburbs and eastern suburbs once the afternoon sea breeze kicks in," Weatherzone meteorologist Brett Dutschke said.
"Anywhere west of the CBD may not see the sea breeze at all, at least until the evening.
"There could be a temperature contrast of eight degrees between the bay and western suburbs."
Ipswich's hottest September day on record came in 1943, when the mercury climbed to 39.2 degrees on the 22nd.
Brisbane recorded its hottest September day in 2008, when it reached 35.1 degrees on the 29th.
Temperatures in parts of far north-west Queensland, including Century Mine, are due to nudge 40 degrees on Wednesday.
"It's going to be fairly dry heat right across the state," Mr Dutschke said.
The conditions have firefighters on high alert.
Roma, Longreach, Blackall and Charleville are at most risk, with wind gusts set to reach 40km/h and humidity likely to remain about 10 per cent, Mr Dutschke said.
Peter Varley from the Rural Fire Service advised residents across drought-affected Queensland to remain vigilant.
"We would ask people to be very vigilant and to be extremely careful with any welding or that sort thing that can produce sparking," he told 612 ABC Brisbane.
The fire danger has eased in NSW where fire crews spent the night battling blazes in Sydney's north-western fringe and parts of the Blue Mountains.
A home was destroyed and seven firefighters were injured when four major fires ravaged the areas of Winmalee in the Blue Mountains, Marsden Park in Blacktown, Castlereagh near Penrith, and Windsor, on Tuesday.