When it is colder outside, I noticed that the CFLs in my house and the fluorescent lights in my garage take longer to come on and get bright. Sometimes they flicker more. I am in Florida so coldest is probably 30-40 degrees in the Winter. Why does this occur? CFLs are in a standard outlet. Fluorescents are in an older ballast.
When turned off, the mercury in the fluorescent tube condenses on the inside surface of the tube. In order to emit light, the mercury must evaporate and form a vapor as the conductive path between the ends of the tube. The colder the bulb is to begin with, the longer it takes for all the mercury to evaporate, and for the light to reach full brightness.
This also explains why fluorescent lights get dimmer as they age: there is a small leakage of mercury from the tube during its lifetime, so there is less mercury vapor in the tube, so less light produced.