Tuesday, Christmas Eve and Christmas Day are tipped to be sunny with only partly cloudy conditions, according to the Bureau of Meteorology.

From Boxing Day, rain becomes more likely, with a 40 per cent chance of showers and an afternoon thunderstorm predicted.

Rain and possible thunderstorms are a 60 per cent chance during the next three days.

With conditions ideal for barbecues and outdoor activity in the coming days, Queensland Health's Dr Mark Elcock urged the public to stay hydrated and look out for those more vulnerable to heat-related illness.

These include infants, the elderly, pregnant women and people who were overweight or obese.

Mr Elcock provided the regular tips for staying cool - drinking water throughout the day, staying in air conditioned areas on hot days and taking a cool shower.

"I would be avoiding alcohol and caffeine drinks," he said.

"The high-energy drinks aren't the best when you're trying to get your fluids back up. It's not just water, it's your electrolytes and salts that are part of your body system that are important.

He said symptoms of heat illness started with being thirsty, before progressing to headaches, muscle cramps, dark-coloured urine being passed, hot skin, a rapid pulse, irrational behaviour and eventually falling unconscious.

"There's certainly a direct correlation with prolonged periods of high temperatures, with triple-0 calls and presentations to emergency departments for people with heat-related problems," he said.