Brisbane heats up for G20

The mercury is tipped to reach almost 40 degrees in Brisbane as world leaders gather for the G20 summit this weekend.

The weather bureau predicts records will be smashed as an extreme heatwave hits the state, with especially hot conditions forecast for the southeast and western regions.

"We have what we would call an extreme heatwave over the next few days," Bureau of Meteorology forecaster Tony Wedd told AAP on Friday.

Temperatures will reach 35 degrees in Brisbane city on Saturday when the G20 Leaders' Summit kicks off, and a sweltering 39 on Sunday.

Average peak temperatures for Brisbane in November are around the high 20s.

Ipswich, west of the city, is expected to tip 42 degrees on Sunday and the Sunshine Coast, Gold Coast and Wide Bay Burnett regions, as well as adjacent inland areas, will experience soaring temperatures.

Concerns have been raised over how police officers and protesters in Brisbane for the G20 will cope in the extreme heat.

Queensland Health Chief Health Officer Jeannette Young says it's important people stay cool and hydrated.

"The effects of overheating on the body can vary from heat rash and cramps through to heat exhaustion or heat stroke," she warned.

Dr Young urged people to keep an eye out for each other, especially those more vulnerable to hot conditions such as children, the elderly, pregnant women, and overweight and obese people.

Symptoms of heat exhaustion, which usually develop over several days, include muscle cramps, heavy sweating, paleness, dizziness, nausea or vomiting and fainting.

Residents, particularly those in the west and southeast, have also been urged to be vigilant as an extreme to severe fire alert is in place across much of the state.

Temperatures are expected to cool by Monday, although hot conditions may persist in the Wide Bay-Burnett region.