Summer's finally here. Most Kiwis welcome it like a comfy pair of old sandals, but if you don't know your sun alphabet you could end up like a barbecued prawn.
We've become familiar with UVR and SPF. Now D has been added to the mix.
For those of you who've been living in a cave for the past decade - or even the Northern Hemisphere - UVR is ultraviolet radiation. It's the burning rays given off by the sun.
UVR levels are about 40 per cent higher in NZ than at places at the same latitude in the northern hemisphere because of clearer skies, less ozone overhead, and the Earth's elliptical orbit placing us closer to the sun in our summer.
The Cancer Society says too much UVR can lead to sunburn, premature skin ageing, and skin cancer, including the sometimes deadly melanoma.
SPF, or sun protection factor, is used to describe the shielding effect of suncreens against burning.
An SPF 15 means the product will give you 15 times more protection than using no sunscreen.
D is the vitamin created by the action of the sun on our skin.
It works like a hormone, with an important role in bone and muscle health and regulating calcium levels in the blood.
Vitamin D has been in the news a lot lately. It's at the centre of the latest balancing act we Kiwis have to perform, between getting enough sun but not too much.
"Vitamin D made by getting sunlight on the skin is essential for sound bones and general health," the Cancer Society's SunSmart advice says.
The Ministry of Health's guidelines on vitamin D say that at the extreme end of the spectrum a deficiency can lead to rickets in young children, causing bowed legs and knock knees.
In adults, deficiency can cause bone weakness and increased risk of fracture. Adults with vitamin D deficiency may be diagnosed with osteomalacia ("soft" bones). However, what constitutes the optimal level of vitamin D is currently the subject of international debate.
During spring and summer, a few minutes of sun on the face, arms and hands on most days of the week outside peak UVR periods - that is, before 11am or after 4pm - is thought to be enough to produce adequate vitamin D.
However, people with dark skin tend to need more time in the sun - perhaps three to six times more, the Cancer Society says. It is important to note though that many people with dark skin report getting sunburnt and still need to protect themselves during peak UVR periods.
Between 11am and 4pm, the fair-skinned should have an arsenal of protection: shade, sunhat, sunglasses, clothing that covers most of the skin, and a broad-spectrum sunscreen with an SPF of 30 or more on exposed skin.
In the winter, protection against the sun is not such a priority unless people with fair skin are in reflective environments such as snow, sand, or water, or outside for long periods.
Dark-skinned people may need vitamin D supplements in winter, but should consult their doctor if they are concerned their vitamin D levels may be low,
Cancer Society Otago/Southland health promotion manager Penelope Scott says people vary in their ability to make vitamin D. It's difficult to know with any certainty whether those in southern New Zealand can make enough in winter because this depends on various individual and lifestyle factors, such as skin type, age, or whether they work or spend a lot of time outdoors. Moreover, the science is still far from clear about the role of vitamin D and various health outcomes, aside from its role in bone and muscle health.
The Ministry of Health says that 3 per cent of New Zealand adults have vitamin D deficiency, but the optimum level is under debate both here and overseas.
The best way to check your vitamin D status is to discuss it with your doctor, the ministry says.
There's no way it can provide a guideline for how much sun everyone needs, it says. "This is because the amount of sun you need to make enough vitamin D depends on factors such as your skin colour, age, and dietary intake of vitamin D, as well as the season, time of day and geographical location.
"You may be able to increase your vitamin D status by increased sun exposure (before 11 am or after 4 pm) and by choosing foods that contain vitamin D."
Small quantities occur naturally in oily fish such as salmon, tuna, sardines, eel and warehou, milk and milk products, eggs and liver.
The ministry recommends a vitamin D tablet of 10-25g a day for people with vitamin D deficiency. They may be house-bound, don't regularly expose their skin to the sun, have darker pigmented skin, or be infants exclusively breastfed by a mother who is vitamin D deficient.
For further information, check out the ministry's online Food and Nutrition Guidelines for Healthy New Zealanders.
Skin Cancer is largely preventable by being SunSmart during those times of the year and day when UVR levels are high. It is important to avoid getting sunburned. Skin can burn in as little as 15 minutes in the midday summer sun.
When to be SunSmart:
Between September and March, especially from  11am to 4pm when UV radiation levels are very high.
Slip: Slip on some sun-protective clothing,such as a shirt with a collar and long sleeves, and trousers or long-legged shorts.
Slop: Slop on SPF30+ sunscreen 20 minutes before you go outdoors and every two hours afterwards. But remember that sunscreen should never be your only or main method of protection.
Slap: Slap on a hat that protects your face, head, neck and ears.
Seek: Seek shade whenever possible.
Wrap: Wrap on some sunglasses. Make sure they meet the Australian/New Zealand standard.
Avoid sunbeds: Using solaria increases your risk of developing skin cancer.