While rain and cloud will arrive shortly, we are still getting highs of up to 29C in Auckland, and temperatures exceeding 30C in Gisborne, Hawkes Bay and Wairarapa.

With the hot muggy temperatures expected to stick around until Thursday or Friday, we take a more serious look at protecting yourself and family members from some of the less visible threats of summer.

UV light

The greatest risk to our safety during summer is the sun.

The six-billion-year-old star emits a number of ultraviolet rays, some long-wave (UVA) and other short-wave (UVB and UVC). UVC is mostly absorbed by the ozone layer due to its shorter wave-length.

READ MORE: Unbearable heat and humidity
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UVA penetrates deep into the skin and causes ageing, but contributes less to sunburn. UVB presents the most immediate risk to sunburn and skin-cancer.

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Ultraviolet light is an invisible killer. There is no way to tell you are getting burnt - ultraviolet light cannot be seen or felt. The only way to prevent UV rays burning is through precaution - shade and sunscreen.

UV rays are also responsible for cataracts and eye cancer, our eyes need as much protection as our skin.

Exposure to UV is responsible for 90 per cent of skin cancers. Children as young as 8 years old are being diagnosed with preventable skin cancer in New Zealand.

Getting burnt can still increase your chances of getting skin cancer by up to three times.

The reddish look of sunburn is caused by blood vessels swelling around the damaged DNA to allow blood to flood and repair the area.

If you have a peeling sunburn, that means your body has absorbed so much damaging radiation that your body attempts to shed the affected cells.

Just as a person would not willingly stay near a nuclear fallout zone for fear of contamination, we must protect ourselves from cancer-causing radiation damage from our sun.

Humidity

A heat-wave with humidity is a lethal combination and it doesn't just affect tropical areas. Heat-waves in Russia and Western Europe in the past decade have been responsible for thousands of deaths and, as the earth heats up, they are becoming a more pertinent risk to New Zealanders.

Even if temperatures aren't extreme, high humidity can present a real danger.

The body cools itself by losing water through the skin (sweating), or at the very extreme, by panting.

The cooling function of sweating comes from the water being removed from the skin through evaporation - water then drips over the skin, cooling it down.

High humidity can defeat the evaporation system meaning sweating will not work. Instead we have the normal dehydrating effect of perspiration without the cooling, leading to heat-related illness and even death.

At extreme humidity pressure, a human being will die in roughly six minutes without cooling.

It's important in extreme heat to maintain hydration and cool the body. A swim or cold shower can provide relief and lower body temperature.

Those planning to do outdoor sports should carry plenty of water and stay close to inhabited areas and amenities in case dehydration or heat-stroke occurs.

Water

Water safety is repeatedly drilled into New Zealanders as a major concern, yet we still have a substantial drowning toll each year.

Our beaches are fantastic but unforgiving and unpredictable places. While it might be nice to get away from the masses, swimming between the flags is your safest bet

It's important to stay calm when caught in a rip and not fight directly against it. If you're being dragged away from the beach, swim at an angle until you're out of its grip; if you're being dragged sideways, remain calm and swim towards the beach.

Many people panic because they feel the rip is pulling them under. But there are no ocean currents that pull you under.

A strong rip can pull a person out to sea at the same pace of an Olympic freestyle swimmer - swimming against the current will expend massive amounts of energy without covering the distance to safety.

If you're worried you've been caught in a rip, put your hand up and tread water. Lifeguards will make their way to you.