Sun exposure doesn't increase the risk of getting Malignant Melanoma. It probably reduces it.

Wait, WHAT?!?! I've done it again!

Here comes the sun, doo doo doo doo.

According to Does solar exposure, as indicated by the non-melanoma skin cancers, protect from solid cancers: vitamin D as a possible explanation,
"Vitamin D production in the skin seems to decrease the risk of several solid cancers (especially stomach, colorectal, liver and gallbladder, pancreas, lung, female breast, prostate, bladder and kidney cancers). The apparently protective effect of sun exposure against second primary cancer is more pronounced after non-melanoma skin cancers than melanoma, which is consistent with earlier reports that non-melanoma skin cancers reflect cumulative sun exposure, whereas melanoma is more related to sunburn."

See also Is Vitamin D Shooting Me in the Foot?

Insufficient sun exposure increases the risk of getting cancer. This isn't surprising, as cancer cells are constantly being produced in our bodies due to defects occurring in DNA etc. Our immune systems destroy them. Only when cancer cells manage to evade the immune system (by pure chance) does cancer develop. An immune system weakened by Vitamin D insufficiency is asking for trouble.

Excessive sun exposure increases the risk of getting skin cancer. Chronically-excessive sun exposure (outdoor workers) increases the risk of getting Basal Cell Carcinoma & Squamous Cell Carcinoma.

Acutely-excessive sun exposure causing sunburn (holidaymakers) increases the risk of getting Malignant Melanoma.

Combining insufficient sun exposure for 50 weeks of the year with acutely-excessive sun exposure for 2 weeks of the year is really asking for trouble. What makes the situation even worse is that Vitamin D insufficiency makes the skin burn more easily.

I take 5000iu/day of Vitamin D3 and my skin is far more resistant to burning than it used to be. I can go for long drives on a sunny day with the top down and not burn. My face goes pink, but that's all.

I've already read on Facebook about friends burning themselves to a crisp in the wishy-washy May English sun. It's not sun exposure that increases the risk of getting Malignant Melanoma. It's ignorance, apathy, stupidity and/or bad luck.

Be careful out there!