Lady, EVOLVED 
does the temperature being higher actually increase the amount of UV radiation output by the sun or are people just conflating those two for some reason
@Lady idk about temperature but https://www.fda.gov/radiation-emitting-products/tanning/ultraviolet-uv-radiation#6 says that there's more in the summer: «The sun’s angle in relation to the Earth varies according to season. During the summer months the sun is in a more direct angle, resulting in a greater amount of UV radiation.»
(with https://www.epa.gov/sunsafety/sun-safety-monthly-average-uv-index seeming to confirm that point)
@alyssa europe is evidently currently experiencing a heat wave so lots of people on masto are making posts with advice to people unused to the heat
@Lady hmm, yeah, that would also be my intuition. i am unfamiliar with the context this is coming up in.