Authorities have issued heat health alerts for parts of central Victoria on Thursday, and the entire region on Friday.

Bendigo is forecast to hit 40 degrees on Thursday and 43 on Friday, with minimums of just 23 and 24 overnight.

Heat health alerts have been issued for the Northern County and Mallee on Thursday and Friday, and the North Central District on Friday.

Read more: Forecast sees partial extreme heat timetable on Wednesday

The Department of Health and Human services puts out these alerts when temperatures exceed the threshold above which heat-related illness and mortality increase substantially.

Older people, young children and those with a medical condition are more at risk from extreme heat, but it can affect anyone.

Heat stress takes place when the body cannot cool itself enough to maintain a health temperature.

Deterioration of existing medical conditions is the most common health problem caused by heat stress.

Symptoms of heat related illness in young children and babies include restlessness, irritability, and fewer wet nappies. Older people may become lightheaded, confused, weak or faint.

OTHER NEWS:

To reduce the risk of heat-related illness, drink plenty of water, reduce exposure to heat, protect yourself outside, plan to avoid activity on hot days, avoid leaving children, older people or pets in cars, rest whenever possible, stay cool and check in with others.

More information about preventing heatstoke is available on the Better Health Channel.

For medical advice contact your doctor, or Nurse on Call at 1300 606 024.

In an emergency, call triple zero (000).

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