Health experts have warned Queenslanders to take care as severe and extreme heatwave conditions blanket much of the state.

Parts of southern Queensland sweltered in the unseasonal heat, which extended north to Mount Isa and west to Birdsville, the Bureau of Meteorology said on Monday.

In the channel country, the mercury reached 43.4C at Thargomindah about 1.30pm, while Windorah hit 43.3C and Ballera peaked at 42.2C. Closer to the coast, St George reached 42.6C at 2.30pm, while Charleville hit a maximum temperature of 41.9C.

Queensland Ambulance’s director of clinical quality and patient safety, Tony Hucker, said people can become ill very quickly on hot days, particularly if they are working hard.

“If you’re outside, if you’re in the sun and you’re not keeping your fluids up,” he said.

Queensland Health urged people to take precautions against dehydration and other heat-related conditions, by staying cool and drinking water.

Parents of infants, the elderly and people with some pre-existing medical conditions were warned to be particularly cautious, as were pregnant and breastfeeding women, and obese people.

Heat-related illnesses include heat rash, heavy sweating, dizziness, nausea, vomiting and fainting.

Closer to Brisbane, Ipswich failed to reach the forecast 39C on Monday, peaking at 36C about 1.30pm. Conditions are expected to remain extreme in Ipswich with 40C forecast on Tuesday and 39C on Wednesday.

Elsewhere, severe weather conditions will continue until Wednesday afternoon when a strong cool change is expected to move through the southern half of the state.

However, the heatwave conditions are expected to persist in north Queensland.