Just some advise

1. Since you are talking two completely opposite thing: hot/raining and cold, using 卻 would sound better than using 也. 卻 indicates oppositeness while 也 indicates additional information that is as important as the given one.

2. Using 才 here is better than using 就. "A 就 B" suggests that if A happens, B also happens, while "A才B" suggests that only if A happens, B happens. Since I believe you wanted to say only summer of 35 degrees is true summer for you, 才 sounds better.

3. 在 and 再 have identical pronunciation, but completely different meanings. 再 means "repeat, again, or after which", while 在 means "at, on, in". Normally, it is 在 that is being used with location or time.

For your reference,

"再+Verb" means to do something again, or to do something after the condition precedes this.

"在+Verb" means to be doing something.

夏天 I

夏天 I

夏天 I

                                                                                                夏天 

夏天是我最喜欢的季节,因为我很喜欢热的天气。捷克的夏天有时候燥热，也有时候会冷，也会下雨。很多人不喜欢热的天气 但是对我来说，暖热的夏天（35度多）才是真正的夏天。在捷克，学生有两个月暑假 –  七月和八月。 小的时候，每年的暑假，我和我弟弟都会在南莫拉维亚（一个小村庄）的爷爷奶奶家过上几周。 南莫拉维亚的天气比较暖和， 夏天太阳很足。我和我弟弟每天都会花大部分时间在外面玩儿或者帮助爷爷奶奶做些家务。

中文很不错，继续加油！