I don't have mods about weather. But in normal play, you can set the seasons to 7, 14 or 28 days. If you want the four seasons to rotate fast you can set them to 7 days each. Summer (and all seasons) are not all sunny. It can rain and there can be storms. While there's a pattern, seasons aren't always the same. This year summer may be full of hot waves and next year's can be more rainy. You also can buy (or build, i dont know for sure cause i never used it) a weather machine and with that influence the weather. I know i've come across some mods that allow you to use the weather machine without the requirements.