I have put compact flourescents in some cold weather locations and noticed that they take some time to come up to full brightness and the question hit me, is there a temperature where they won’t work at all? how about LED bulbs?
There has to be someone out there that knows and this seemed to be the place to ask.
No idea of the answer, but I do know that I took the CFLs out of my porch lights, and put incandescent bulbs back in, because the weak candlelight-level light for the first few minutes in the wintertime was absurd.
I don’t know if there is a temperature where CFLs won’t work at all, but if there is, it’s probably below the freezing point of Mercury, -38. LED lamps don’t have this issue, and will work at full brightness down to very low temperatures (at extremely low temperatures the electrolytic caps in the power supply might freeze, and get destroyed).
Now that you mention it, we had low-energy bulbs in our front door light in our last house, and they always stopped working when the temperature got too cold (around -25ºC, if I remember correctly), and we had to put old-style incandescent bulbs back in.
If a mod wanted to fix the spelling in the title, I’d be eternally grateful (that’s one of my nails-on-a-chalkboard errors). 
one particular CFL in front of me is 0F. i haven’t done a search, though they can go to -10F i recall.
CFL are also best if left on for 30 minutes or more. if you need immediate brightness or short duration use then another illumination device might work better for you.
I’ve got CFLs in my outside lights, and they’ve been working at sub-0ºF temps this winter. It’s supposed to get colder than that over the next few days. If I remember, I’ll see if they will start up.
I thought some CFLs came up to full capacity more quickly than others. It seems to me some in our house come up to capacity almost immediately and others require a second or two.
This is definitely true.
Newer (electronically ballasted) CFLs of 23W or less come up to full brightness almost immediately. Higher wattage ones still take a few seconds, but they’re plenty bright at turn-on. Older CFLs were much slower. It also depends on the manufacturer. I find that the really cheap ones that Home Depot sells work great, turning on instantly.
I second that - I have put halogen bulbs (from IKEA) which use 1/3 less watt than old-style bulbs in my floor and bathroom, because I need light immediatly there, but only for a short time.
In the living room and on my work desk, everything is energy-saving tubes because there the lights will stay on for hours, so it’s worth it.
Found this tidbit on Wikipedia. Summary: hybrid CFL’s are now available that use an incandescent element to provide instant-on light, which shuts off when the CFL element reaches full operating temp/brightness. Best of both worlds, if it works as advertised.
The cold weather is here. These are 3 - 3 year old “swirled” CFLs that hang in carriage lamp style lights (socket end up). One is attached to the house, and is sheltered, two are on the unheated garage, and out in the wind.
This is what has happened.
10ºF - Lights comes right on, but are a bit dim for a couple of minutes. They start out at maybe the equivalent of a 30W incandescent bulb.
0ºF - Lights come right on, but start out looking like a bright nightlight for maybe a minute, than a couple of minutes at the 30W level. By 5 minutes, they are up to full strength
-10ºF - Lights hesitate momentarily when turned on. One of the bulbs on the garage was brighter on the bottom (away from the socket) when first lit. The dimmer part barely lit up the garage wall it is mounted on.
So I haven’t found the “will not light” temperature yet. If I wanted to be able to read on my front porch as soon as I flipped the switch, CFL would not be the way to go in the winter.
I have CFLs in the outside lights, and the temperature often get down as low as -20ºC to -30ºC in wintertime (-5ºF to -22ºF). I find the lights are somewhat dimmer at low temperatures, but not significantly so (the occasional -40ºC/F day dims them a lot, though). Our lights are on 24/7 however, so results might be different for ones that are turned on and off.
Early CFL’s were indeed limited at in chilly weather – they were slow to start & dim at first at 20ºF, and sometimes wouldn’t work at all a -10ºF or colder. But now there are ‘cold-weather’ CFL’s that work reliably down to even fairly cold temps, like -20 to -30ºF.
However, they are more expensive than regular CFL’s. LED’s work regardless of the temp, but they are even more expensive now.
My security lights have 2 sockets, so my cheapskate solution was to use 1 regular incandescent floodlight and 1 CFL floodlight. The incandescent comes on at full brightness immediately, while the CFL takes a minute or 2 to reach that level.