It should never be warmer than 84 degrees Fahrenheit. (Or 29°C if you prefer.) There is just no reason it needs to be any hotter than 84°F. Ever. It is completely unnecessary that the temperature ever approach 90°F. And 100°F? Just go on and get all the way the heck out of here with that nonsense.
Anything warmer than 84 and there is just no reason to do anything. It's around 85 where you can break a sweat just walking outside. The sun is a little too intense. Like, come on sun. Just take it easy. Can you just be cool? It's too hot to stand next to the grill. Golf is less fun. I'm worried about the kids overheating.
And 84 is just the max we need to agree on. The actual best temperature for a warm day is somewhere in the low 70's. Probably 72°F. Maybe as low as 69°F. You step outside in the low 70's and the sun almost feels welcoming.
Of course, you add a little humidity to any of those temperatures and your day is ruined. Most people forget this, but it's actually the humidity that gets you. Who invented humidity anyway? It's bad. Bad. You show me somebody who likes humidity, I'll show you a crazy person.
If we're talking real, perfect, best weather, we're talking hoodie weather. Right around 60°F. A little cooler if the sun is out. A little warmer if it's cloudy. You get the temperature around that and you'll be damn near barbecuing.
Unfortunately, it is summer so even talking about hoodies is pointless. The way 2020 has gone they might extend summer indefinitely and cancel fall this year. So we have to settle for warmer weather and deal with temperatures that cross the line from perfectly acceptable to way too hot. So let's just agree to keep it 84 and everyone can at least deal with the heat. Cool? Not quite, but cool enough.