How much water should you drink in a heat wave?

As summer rolls across New Zealand, driving Kiwis into the shade, the question we should all be asking ourselves is: "Am I drinking enough water?"

Overseas, the death toll can rise into the thousands when a heat wave hits.

While New Zealand escapes the worst of these effects, the temperature increase can be dangerous for pets, children and the elderly.

As the mercury rises, your body increases its amount of perspiration to keep your internal body temperature at a stable level.

But as your body runs out of water, dehydration starts kicking in, causing headaches, dizziness and confusion. The worst case scenarios can be life-threatening - including heatstroke, seizures and hypovolemic shock.

So how much water do you need to stay safe?

It's recommended we drink six to eight glasses of water a day - but this increases dramatically in hot weather.

During heavy exercise in a hot environment, drink two to four glasses of cool fluids each hour.

The Arizona Department of Health Services - experts in treating people in extreme heat waves - warns people outdoors in dangerous heat can need one to two litres per hour.

The good recommendation is to use the colour of your urine as an indication of how dehydrated you are. If it's a dark colour you need to drink more water.

Other advice includes having a heat wave action plan, staying hydrated, avoiding alcohol and limiting physical activity.

Last year was New Zealand's hottest since records began more than 100 years ago. This year is likely to be in the top three if not the hottest, according to the World Meteorological Organisation.

Newshub.