1.I guess you want to say "the weather in/of Moscow is very hot" ,but in Chinese "of(A is under the definition of B" and "in(A is inside or during the time range of B" is different word, so either you can say "莫斯科的天气非常热" means the weather of Moscow is very hot, or "莫斯科在夏天非常热" means the Moscow is very hot in summer.
2. Like English, Chinese also have such grammar "whenever xxxx, I will/I'd like to..." and in this situation, we need to add "会" to clarify what is your wish.
3. Lost subject, what you said is the night can siting around bonfire.