It’s not safe.
There’s a common misconception that sweat training helps one lose weight. In reality, it’s actually horrible for you. When you sweat, you’re losing the necessary water your body needs, which is why as runners we always talk about how important hydration is.
General rule of thumb: for every pound you lose on a run, you drink an ounce of water after. For example, if you get back from a run and are 2 pounds lower than before, you need to drink at least 2 ounces of water to replenish.
I’m not sure what is different this year, but I have run into so many people running in spandex and jackets on these 70-90 degree days. Dehydration can lead to many other serious issues, such as overheating and heat stroke.
As temperatures rise, it’s very important to keep track of your liquid consumption with how much you’ll lose on a sweaty run. If you know someone who sweat trains, try to talk to them about these important health issues.