I've ridden in 15F with a ski helmet and goggles. Low temps in the high 20's are usually the worst I ride in.

I rode 28 miles in 50 °F today. Temperature wasn't an issue at all during the ride, but something I've noticed about riding in cool weather is that after the ride, by jaw has become stiff. For the first few minutes after the ride, my speech is slurred. Doesn't happen in warm weather....

^^^Add less vodka to the Powerade next time and that will go away^^^

There's no bad cycling weather, just bad clothing choices.
Around here, it doesn't often get down to 0 degrees f,(-18c), but I do ride at that temp when it does.
Full face covering and ski goggles are a must.
A couple of years ago, I was working in the Northwest Territories for the winter. Believe it or not, there are people who ride their bikes all winter in Yellowknife. I was not one of them.

I voted -10°F.

The coldest it's gotten here in the last two winters is +4°F. I've ridden then just fine. Okay, it's a bit chilly. Judging from that, I'm taking a stab at -10.

Since botto is currently on the bad guy list let me contribute this to the discussion:

incorrect

I don't like anything under 40 degrees. But, since I'm commuting now, and the Stratus XP I'm riding on the commute has a fairing, and even against a wind, it's only about an hour to work, I'll probably still ride in the 30's this winter.

Unlike cars, bicycles will start no matter how cold it is. Growing up in Connecticut, I went for a ride at -20 F. It was fun because yhere were no other vehicles on the road that day. I often go downhill skiing at -30 at Tremblant, and it is no problem with the right clothing. Around here though, 0 F is the coldest it ever gets and below 10 F is rare. I never check the weather -- just throw on overpants, coat, boots, and gloves, hop on the bike, and off to work. After I arrive, I find how cold it was.

Paul

I went out a couple of times recently at 41F for about 20 miles. It was sunny and there was no wind to speak of. I layered up and did fine. I need to get some glasses to keep my eyes from watering, though. Also I carry a big bandana for the nose issues.

Although I've not ridden in the Carolinas at that temperature, I was at 20>. When I lived in west suburban Chi. town, we had a group that would ride on the Illinois Prairie path at night when it was frequently below freezing, and yes, clothing choice was the critical factor for comfort. We also rode on New Years Day as a "tradition" like the Polar Bear Club swimming in Lake Michigan!

I voted +32 even though last year I rode when it was in the upper 20's. I am thinking that I can not find what I need to keep my toes warm below 32 so there it is +32.
Layers are your friend.
Was any of this low temp riding fun? Well ....I can not really say it was fun but I did it and more than likely will again.

I've been riding in foul weather, in the cold down to single digits for years and recently in rain, and I have come to the conclusion that foul weather riding is tolerable for me at least, for ten miles, and you endure the rest. My commute is 14 miles long.

Around 11 degrees was my coldest ride last winter....gotta try for a sub-zero this year....no guts,no glory!!!!

I picked zero only because that's as cold as it ever gets here. Long as the roads are clear of ice and snow, I'll be out there. As my Norwegian relatives say, "There's no such thing as bad weather - only inadequate clothing."

SP
Bend, OR

I'll ride down until it freezes over. Given that this is the Seattle area, it (1) almost never gets that cold and (2) never stays there for very long. At most I've had to take a couple of days off.

The coldest temps I've ridden in have been in the low 20's. I'm okay with everything except my toes. The new gloves I got last winter completely solved my finger issues. Now I just need to figure out how to keep the toes warmer at those temps-although the "toe warmers" help a lot.

As a daily, year round commuter, I voted 0F since the coldest temperature I've seen in the DC area in my two years of daily commuting was 8F. However, my coldest ride during that time was at 14F (had a cold and stayed home from work for the two days when it was below 10F for the morning commute). I figured I could go a few degrees colder with what I've got. The ride home should be at least around freezing.

I'll commute into the 20s ... fun rides, into the 50s.

Cold is not fun.

Do tell, please.

I have often wondered if those "toe covers" worked. Should I get them or shoe covers?

I live in the most temperate corner of Canuckistan -- still, this is the Great White North. We do winter cycling here.

My record is 17.6 degrees F according to KASG, a nearby weather station. I voted for +20. Windchill was 5. It was a night ride. I looked like the Michelin Man. Did the ride just to see if I could ride and survive at that temp. I'm with JPPE on this one. Keeping the feet warm is my biggest issue with cold weather rides.

last winter I started riding in February when the temps warmed up to the 40s which wasn't too often and the roads were disgusting and my bikes got filthy

The coldest I have ever ridden was 2/14/2004, -4F/-20C. That was my regular morning commute, 8.5 miles. 2 days later we got down to -8F, but I was traveling out-of-state that day and drove instead.
Since I have osteoporosis I have given up riding when it is icy, so I don't get as many cold rides in as I used to. I always found that at single digit and lower temps, drivers were a little more courteous, probably they just are afraid of the crazy lady on the bike.