How about Philips 18 watt SL/O "Outdoor" "Earth Light"? That one starts in temperatures down to even a little below zero degrees F, about -20 degrees C. In windchills as low as a few degrees F (around -15 C), this one warms up most of the way to full brightness, but may take several minutes to do so and can start very dim and even start with an "off" pinkish-red color. In fixtures that protect it from wind, it can warm up most of the way in temperatures a few degrees above zero F (or -15 degrees C). In enclosed fixtures, once it starts it can accumulate heat and warm up most of the way in temperatures a little below zero F (approx. -20 degrees C). In an enclosed fixture, this one should work outdors in anything short of the worst couple nights of an average winter of Chicago!
There is at least one lower wattage in the Philips SL/O series, but it appears to me that specifically the 18 watt one is the good one.
If you want Cf lamps that are good in higher temperatures, then the 15 and 20 watt Philips SLS ones are good. I have seen the 15 watt one dimmed by drafts, and these two (and not the 23 and 25 watt ones as far as I know) are rated for use in recessed ceiling fixtures.
For good efficiency in indoor use, any of the above are normally good, but in favorable environments I believe the Sylvania Dulux EL series does even better.
For good fit that requires an overall length not much longer than that of regular incandescents, the spirals do well. Watch for some specific unreliable models better known by wattage: 25 watts (probably discontinued by now), which I found prone to dying very young whether of the the much-maligned (often deservedly so according to my experience) Lights of America brand, or of the GE brand (one of the "Big Three" and mostly reputable). There are two sizes of 24 watt, the smaller one of which is "mini" and I had one of those die young. But most other spirals seem to do well. My apartment building has had about 4 dozen 15 watt ones imported by Abco and having the "Westinghouse" brand, and about 40 of them are still alive after 22 months running 24 hours a day.
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- Don Klipstein ( snipped-for-privacy@misty.com,