TV weather people saying that the temp will be in the 80s is less useful to me than if they tell me if it will be 27°C for example

Well this isn't really an accurate comparison. If they know an exact temperature, they would say it in both measurements. But they don't. So "in the 80s" is the perfect range. Preparing for 80 degrees is almost identical to how you would prepare for 89 degrees. There's no metric equivalent. The "20s" is way too big of a range. 20 vs 29 is a huge difference. Also, with it being base 10, you don't really need more information. 80 is 80% hot. Think of the hottest weather you've been in. 80 degrees is about 80% of that. And before you say "I've been in 115 degree weather". Yeah, so have I, I lived in arizona, and 115 is honestly not too much different than 100. After 100 it doesn't matter much. Same with below 0. But the 0-100 range, each degree matters quite a bit