The Lismore temperature is predicted to hit 36 degrees today, and in some parts of the state, it's predicted to reach the mid-40s.

So, NSW Health is again reminding people to take necessary actions to keep cool to avoid overheating.

NSW Director of Environmental Health Dr Richard Broome said the combined effects of persistent bushfire smoke and soaring temperatures means vulnerable people should take extra precautions.

“Hot weather and poor air quality are a recipe for severe illness unless people take simple precautions,” Dr Broome said.

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“We are urging people to avoid being outside during the hottest part of the day, to minimise physical activity, to keep well hydrated and reduce their exposure to smoky air.

“Hot weather puts a lot of strain on the body, causes dehydration and can make underlying health conditions worse. It also causes heat stress and heat stroke.

“Compounded by the continued impact of smoky air from bushfires, it’s important that people are prepared, particularly people with underlying medical and respiratory conditions.

“It’s best to stay indoors during the hottest part of the day, which is generally from about 11am to 4pm. Staying indoors also protects you from bushfire smoke.

"If you don’t have air conditioning, using a fan can cool you down and keeping curtains shut helps to keep the heat out of your home. It’s also important to minimise physical activity and to drink plenty of water.

“It’s also really important to stay in regular contact with elderly neighbours, friends and relatives because they may be more vulnerable to the heat.

“Signs of heat-related illness include dizziness, tiredness, irritability, thirst, fainting, muscle pains or cramps, headache, changes in skin colour, rapid pulse, shallow breathing, vomiting and confusion,” he said.

Dr Broome said it’s important to get to a cool place quickly if symptoms occur. People showing severe signs of heat-related illness should seek urgent medical attention, in an emergency situation call Triple Zero (000).

More information can be found at the NSW Health website: http://www.health.nsw.gov.au/environment/beattheheat