Recently, Germany it has been burning hot in Germany with temperatures up to 42°C (108°F)! Unfortunately, A/C is quite rare in Germany. It can only be found in cars, public transport (frequently very weak, though!) and supermarkets. Schools and the like are almost never equipped with A/C. So how can you even learn German, when your classroom is hot like hell? From my experience as a German teacher in Munich, I can give you some suggestions.
1. Drink a lot. This should be self-evident. However, as it is most important, I didn't want to conceal it.
2. Wear clothed made of linen. Linen is very suitable for hot temperatures. I think, that is, because linen is quite permeable to air. Clothes made of linen can be very chic. The alternative would be to wear thin, but we have got too much style to do so, don't we?
3. Get your own portable, personal fan. I can recommend this one: It's very affordable with great performance.
I hope, my tips will help you to continue learning German with pleasure despite the heat wave!