Listen to the vernacular of this weather report from Las Vegas, a desert. The report claims a man got 3rd DEGREE BURNS from sitting on a bus bench. LMFAO!!
This just after Las Vegas just broke a 60 year old record for the most days under triple digits:
291 Days in a row
I work outside. I haven't used sun screen since I was a teenager.
Skin Cancer is caused by frequency of sun burns. Melanoma rates are highest amongst people with PhDs and lowest amongst farmers, etc. and the same goes for sun screen use.
If you're not used to being out in the midday sun and you have to spend the whole day outside all of a sudden, then high factor sun screen might be a necessary evil. Otherwise low factor (Zinc Oxide) sun screen is the strongest you should ever use, because the risk of benzene compounds is far higher than the chance you'll get a sun burn being outside from 5/6pm onwards.
I just wear regular tshirts outside, if you're in the south you might want something heavier, but a tshirt has an SPF 7~10 and I've gotten a sunburn through one once and it was when I was working beside a foil coated wall sheathing for days, by the time we were done we noticed it had burned an arc into the grass so we'd been in a focal point while working.
I won't get a cold or a sniffle until about november when I've been wearing hoodies and jackets all day to be outside.