The best temperature to be outside is between 70 F to 85 F.
Some people are too hot when it gets above 80 F so you may want to stay inside during those times.
Some people don't find it too hot until it's 90 F or above.
For me it's too hot to be outside when the temperature gets to 90 F or above.
And when the temperature is 100 F to 110 F or above the temperature is way too hot to be outside and you should stay inside.
When it's above 85 F I usually stay inside and don't go back outside unless necessary until the sun goes down.
You can easily get heat stroke and die or get severely ill so it's not worth the risk to stay out in the heat too long.
As for cold weather it's usually too cold to go outside when the temperature is in the 30s F or below.
Even young and healthy people can get sick from the heat if they participate in strenuous physical activities during hot weather:
Limit your outdoor activity, especially midday when the sun is hottest.
Signs of heat exhaustion include.
Cool, moist skin with goose bumps when in the heat.
Weak, rapid pulse.
Low blood pressure upon standing.