You can also leave it out of the fridge after straining if you like.
I like to drink mine cold, so I leave it in the fridge.
I can keep it for a week in the fridge, and it is still fine.
Yes, the colder the weather, the longer it takes to ferment. Just leave it for longer.
It is hard to go wrong with water kefir. If it tastes too sweet, just leave it for longer before trying it again.