The rates are extremely similar once you control for race (which the page you linked allows you to do, by the way). White people get skin cancer at much higher rates than non-white people, because melanin acts as permanent mild SPF, and white people have less skin melanin than non-white people: that's what makes them white, after all. Since Washington is more white than Hawaii, California, and Texas, if you don't control for race it looks — counterintuitively — like Washington is more risky than the others in terms of skin cancer. But it's not, it's just that you're selecting different population demographics.

Also notable is that sunniness doesn't really determine UV exposure; partial cloud cover can actually result in more UV-B exposure, counterintuitively: https://www.drgurgen.com/are-the-suns-uv-rays-really-stronge... And even full cloud cover doesn't completely block UV. So WA and CA aren't as different as you might think.

Meanwhile, as one might expect, most states that get freezing cold for months at a time have lower skin cancer rates than those that don't when controlling for race: if you don't go outside for more than a few minutes a day, while bundled up under multiple layers, for months at a time, well — you see less skin cancer. Some heavy farming states seem to have more skin cancer, but again that makes sense since farm workers are outside a lot.

Vermont and New Hampshire seem like odd exceptions to this rule — but I suspect there's also just some other selection bias at play. UV exposure from the sun causes skin cancer at high rates in white people; trying to make assumptions about states isn't necessarily an easy thing to do, since many other factors are at play when considering who lives where and how much they go outside.

That could have something to do with it, but as someone who lived in WA for quite some time - you don't go outside without clothing for ~7 months in any given year in WA either because it's raining and unpleasant. So that's where this hypothesis falls apart a little. My hypothesis is that constant relatively low level exposure to UV is more beneficial than acute exposure for just a few days / weeks in a given year. I don't have any data to support this hypothesis though.

> you don't go outside without clothing for ~7 months in any given year in WA either because it's raining and unpleasant

Also because one doesn't want to get arrested.

There was (and maybe still is) Solstice parade where people ride their bikes through Seattle completely (or partially) naked. So that's only partially true.