I won't ride my bike if it's going to be colder than......

... around 40 degrees F.

Just curious, because I live in Arizona and it's hardly ever too cold to ride (too hot is another matter, after early morning in the summer!). I have started rides in the very high 30's when I knew it would warm up to at least the mid-40's, and shorter rides that stay in the low- mid 40's.

We're in the middle of an unusual cold snap, and I rode 31 miles Saturday in 42-45 degrees, partly cloudy with some light wind and gusts to over 15 mph. I opted out of a century ride near Phoenix for today because the start was predicted to be between 27 and 30 degrees, with temps in the 30's until around noon. I just don't have the right gear for riding in the 20's and low 30's. Five of my more hardy team mates rode anyway, but said their feet were pretty cold.

So I'm curious about other people's bottom line for cold weather riding.

Hah, I was in Mesa for a few days and managed to get a ride in. DBF said "Are you sure you want to ride? It's 40 degrees right now." I laughed at him.

32-35 is my bottom line, depending on the weather. Due to a muscle injury from 2011 that still gives me problems, I can't ride if it's windy, and I avoid riding if it's wet and close to freezing. I ride mostly on trails that don't get salted and are at least partly in shade, so ice is a concern. So that eliminates a lot of days.

I'm still working on the right gear for the low 30s. My core and legs are fine with what I have, but my hands and feet aren't. I just got some properly-sized shoe covers and lobster gloves, so there's hope, right? Now, if I can find a clear day try it out...

I don't ride for pleasure if it's below 40 F. I'll commute down to 5 F, even though I start complaining around 12 F. But I've spent years amassing excellent winter gear ;) At around 5 F my bike doesn't work very well, shifters and brakes are sluggish, and it's all just too much of a hassle.

Heat bothers me a lot more. I struggle above 80 and at 85 I'd rather not ride anywhere except straight to the beach. I just don't have many coping mechanisms for the heat.

This thread is timely, we have been joking about this very topic lately.....- since I grew up running/riding a bit south of Cleveland, my road riding limit is about 25. Now that I live in Richmond,VA that means I ride outside all year. This has caused varying degrees of amusement and horror among the cyclist/triathlete friends I have who all move to indoor trainers when it is below 45. Actually, the tri club rides on Saturday morning all moved inside in October (when it was sometimes 60....)

My threshold for riding in the cold has moved down in recent years, but this year, it seems to have taken a momentary pause.
I'd say, realistically, I don't go out if it's below 35 and it's not going to get much warmer. However, 30 is my absolute limit, and I have started/ended many rides with temperatures between 30-35.
For me, limiting factors are wind and degree of cloudiness/dampness. Also, road conditions. For example, on election day, it was brilliantly sunny, but cold for early November, maybe 40 at the highest. I rode to vote, about 4 miles, then rode about 18 miles for fun, ending at my client's house for work. When I left to go home (5.5 miles), it was dark, extremely dry and about 32. I was cold the whole time, mostly because I needed my warmest gloves, and I had my mid level ones. It took me awhile to get warm after arriving home.
Yesterday, I chose not to ride outdoors, even with temperatures around 48-50. Why? It was cloudy, damp, and there still was wetness on the roads. That means I'm going to get sprayed and I don't like that. For me, dampness/clouds/wind combined with cooler temperatures really take the joy out of riding. I do it in the summer and fall, and a bit in the spring, but I found that after riding through the winter last year, I like a break in my activities, too, and that's part of it.
And like LPH, I have more trouble with heat.

I moved from Vancouver over 2 yrs. ago, where I did cycle year round, except maybe total of 1 month off bike with winters average at freezin' temperatures. Lowest would be -10 degrees C (14 degrees F).

Southern Alberta is drier air year round but much colder. So if I stuck to AZfiddle's rule, one wouldn't start cycling until June and end in Oct....
So if there is dry pavement with no/little ice/snow, in the winter I bike as low as -18 degrees C (-4 F) and I was doing this every day to work, grocery shopping whenever I had these conditions since this past November. (And winter 2012).

Have cycled as low as -24 C (-11 F) which is a short distance to work or shopping.

I am cycling each trip under 8 kms. when colder than -18. Then back home, same distance. I am cycling as much as possible on bike paths. Believe me, there isn't a ton of people walking on the paths. But our city has a winter policy that does keep our major bike-ped. paths ploughed and snow-free.

What makes it colder in our region of Canada...is wind chill and flat prairie only accentuates wind, cold temp.

Calgary is 2,000 metres above sea level. Vancouver of course is right ...at sea level (if you exclude the Coastal Mountains in the photos of Vancouver area). 3 mountain ranges that run north to south, separate between Vancouver and Calgary (yes there's a ton of mountains to explore or to avoid..)...it is over 1,000 km. east of Vancouver.

As much as I've said I've become a weather wimp.... I don't have a lower temperature limit for outside riding. My factor is black ice. As long as it's safe to ride I will ride. Snow/compact ice is OK - I have tires to handle that, but I do draw the line at black ice. (which we are predicted to have on Wednesday! - areas of freezing fog-)

Current commute (11 mi one way), I'll ride down to about 15 F, that's the point when my feet get too cold despite my best efforts, and it's not cold enough long enough here to buy dedicated winter boots/shoes. It takes some mental fortitude to get out the door when it's 35/raining, but it's worth it to see the co-workers faces when they realize I rode to work :D I'll take the train if it's too icy, since it won't stay cold long enough to bother with the studs the past couple years...

Old commute (2 mi one way), I rode down to about 5 F, it was short enough that the extremities stayed warm....and we didn't get that many days that cold, so I'd challenge myself to do it :)

Non-commute riding, probably 35 F if it's going to be sunny and not super windy.

Of course, it's 55 F and foggy this morning, so I was way too hot halfway to work despite losing several items of clothing from the recent commute wardrobe....

My rule starts with 50o, sunny, and no wind. Once the temps fall below 50, I need two of the 3 conditions to ride. So over the years I've accumulated a lot of warm bike clothes and will pretty much ride down to about 33o as long as it's sunny. However at those temps, I may not stay out much more than an hour to an hour and a half.

I break out my toasty warm Sidi winter shoes at around 42o, and wear Smartwool socks, Terry heavy cold weather winter tights, and 2 layers on top, topped with Goretex shell style jacket, and sometimes a down vest. Smart wool ear warmer or balaclava. PI lobster claw mitts. All this technical clothing is a real game changer for me.

Like Eden, I don't really have a limit unless it is both raining and cold (below 35). We did a 200k this December where the average temp was 41 and it rained for the latter half of the ride (we really thought/hoped it wouldn't rain). That was more miserable than the ride I did a couple weeks later where it was below freezing (but dry) for 3 hours - warming to the late 40s later on.

It depends on the type of ride, and other weather factors (wind, precipitation). Unfortunately, I have a very limited range of comfortable temps. Below 60 and my sinuses really start to act up and I end up with a headache which cancels out any ride enjoyment. A few days ago it went up to 50 (almost a record) and I rode my old bike home from the LBS where it was getting a tune-up and some new life breathed into it. I might ride to the store in colder temps, but only if there isn't much wind. We also get a lot of snow here which obviously makes riding different, but the mounds of snow reduce visibility and passing space. And at the other end, I don't tolerate heat well, either.

I prefer to ride in temps 40 and up - I've cold-air induced asthma and it doesn't have to be THAT cold for me to have problems on the bike. I have ridden in colder temps if there wasn't any wind and lots of sunshine, but I am getting wimpier where this is concerned. I prefer to go hiking or just walking when it is colder.

Not if it's below 15F. We live in Florida for my da (who's a hot weather kind of person), but I love the cold best. :) I like to go outside and do my outdoorsy stuff in the winter, especially in the 25F-45F range. It doesn't get like that often... mostly at night... but I have gotten in a couple rides in this past year that were in the 30s.

I should add that I find riding in rain and just above freezing a LOT colder than riding well below freezing... cold rain har a way of seeping in everywhere.

Under 40F becomes really iffy but more dependent on conditions than a number on the thermometer. The roads or trails must be snow and ice free, I'm not equipped to ride in slippery conditions. I've taken a couple of rides in 30'ish temps and slightly below but it needs to be sunny with no wind and those are short rides just for the sake of getting out. I don't have cold weather cycling clothes and my skiing and ice fishing clothes are too bulky. I don't do either of those sports anymore and confine myself to the indoor trainer when it's 40's F and below. I ride for fun and for me it's just not much fun sub 50's.