When the weather turns cold, it always takes me a while to adjust my kombucha so that it reaches fizzy perfection. It usually ends up taking at least two days longer. Then I discovered that bottling it even if I decant it too early by accident can solve the problem. Give it a few more days and it grows another teeny mushroom in the bottle and fizzifies. The only problem then is the risk of drinking slimy globs of culture, or as Papa Miao likes to call it, “alien snot.” Also, the waiting. I don’t have my kombucha when I need it.
I keep a giant jar of raw sugar for my kombucha and general baking.
Floof in my food 
I still can’t say I’ve tried kombucha..
the stuff in the stores is kind of expensive.
Doesn’t it ferment well in your kitchen? When I had a sourdough starter, I kept it in my kitchen, where there was always enough heat to keep it growing.
I think the reason is this: in the summer, we don’t use the air-conditioning much, so it is a few degrees hotter. and in the winter, we have the heat on all the time but it usually is around 70. Papa Miao and the Miao Kitties are all fans of climate control, though, so they generally veto my ideologically-driven preference for no air-conditioning, but still, I think the temperature differences must be enough to affect the kombucha liveliness.