Summer is warm and not much clothes are needed but is there anyone else who prefers other seasons to have sex outside?

Those who are land locked, and can't get to the ocean coastlines - Beach sex during summer is always just the right temp. The cool seabreeze blowing in keeps temps at a comfy level for some deep, long fucking. If the air is stale, then it will get to warm and it doesn't feel as good, leading back to your original point of being too hot, sweaty and sticky, in all the wrong ways.
(It's highly advised to find a desolate part of the beach, either a nudist area or a hidden cove or area that's not going to get you in hot water with the local prude departments.

That perfect spring temperature window for an outdoor fuck is when the days hit that comfortable 70-ish degree weather. It feels right, not too hot and not chilly either.

Addressing summer, that mid morning before things really heat up is a great time too

How do you avoid sand getting in unwanted nooks and crannies, LOL?

Spring and summer are great for beach sex, for all of the reasons stated by Buck. (With a comfy towel to protect delicate nooks and crannies, lol). But from the perspective of melons -- and more specifically my melons -- I think of fall and winter. Soaking in an outdoor hot tub, with my lower half submerged but my tits fully exposed to the frigid temperatures, my already perky nipples getting and harder than I remembered being possible. Or snuggling in a sleeping bag with my lover, our lower bodies pressed together for warmth but but with me on top of him, exposing my tits to the cold air and letting his hands serve as my tit warmers. Mmmm.

All I can say is AMEN too a beautiful woman! Silky😘