YSK because the first hot spell is when most people discover their AC unit is broken.
Several years ago I waited to turn on my AC. This is how I found out about one of the busiest times for repairmen and had to sweat for two weeks. Now I do a test run a couple of weeks before it heats up. Same goes for the furnace at the end of Autumn.
Edit to add: YSK line (Rule 2)
Floridian here. Anything below 20°F sounds like penguins, and there is no discernable difference between temperatures (eg 15°F ≈ -42°F/C = 🐧🐧).
Idk if I can do a good job, but for me, 10-20 degrees is average winter temp. Nothing to be concerned about: just my winter coat and thin gloves.
0-10 degrees is starting to get cool. If I’m outside for a prolonged period of time I’ll add a hat and switch to my thicker gloves.
-10-0 degrees is cold. That’s the period where breathing through your nose gets crispy and deep breaths make you cough. I always have a hat and good gloves at this range. If I need to be outside for a while, I use flannel lined jeans. I also make sure to use my actual winter boots.
-20 to -10 degrees is rare, but does happen. You really shouldn’t be outside at those temps, but I’ve done it anyway. Any breeze at that temperature is dangerous. A facemask of some kind is strongly recommended if you need to be out for any length of time.
Coldest I’ve personally experienced was -25 degrees. That was winter 2013-14. There’s nothing quite like experiencing that level of cold. I left a university building to go to my jeep with a bottle of powerade in my backpack. When I got to my jeep it had turned into a slushie.
All these temps are absolute by the way; not windchill.