I've never encountered a day that was too hot. There have been plenty of days that were a combination of hot and too humid, but the heat itself has never been a deal breaker for me. I actually prefer the temp to be as hot as possible. The muscles in my legs just seem to wake up and want to play in the hottest weather. It's like my bike suddenly grows a new gear or two.

Learn to embrace the heat and sweat.

I lived in Dhahran / Al-Khobar for 8 years and feel my time there raised the bar for my heat/humidity tolerance. I'd frequently go on 2 hour mountain bike rides in 117-120 degree measured heat with 70-80% humidity.
Our bicycling club would ride at night during the week (when temps would drop to a chilly 104-105F) or at 5AM on the weekends (the sun rises at 3:30-4 AM in Summer).

Mid-July through September are the worst months, as the intense humidity that is generated by the shallow, hot Gulf (98F water temp by late summer) is at its peak.

I spent about a year of my time in Saudi in the desert, which had no humidity issues, and was comfortable riding in temps up to 125F (50C). I did venture out a few times on 55C days (130+).

Despite the time there, and having grown up in Austin, I REALLY dislike humidity. I can handle heat, but far prefer to ride when it is 65-75F.

That's easy, when the wife says it is to hot and won't let me go out for a ride.

Also no limit. This is Fresno... if I refused to ride in 95-110 degree weather, I wouldn't be able to ride . Just take it easy, keep well hydrated, keep a sweat rag on hand, and carry a can of body spray to freshen up a bit.

A few years back, on a hot Sacramento summer day (105° or so), I forgot to pack shorts for the ride home. I rode home in blue jeans, still enjoyed the ride. It's farther now, 12 miles instead of 6, but I still don't think there's really any upper limit

I ride all summer here in MD where 90-100 days are frequent. Make sure to go easy until your used to it and as noted above stay hydrated. Depending on where I'm riding and how long the ride is (sometimes I take the really long way into work) I sometimes wear light long sleeves and pants to cover more skin... being exposed to the sun for longer periods of time is draining.

Biking in Austin means months of 90-110 degree weather. It is hot and very sweaty, but I prefer it to the cold. The only bad thing is sitting at red lights.

My first season cycling. On the way home from work (partial commute) it was 96F (per weather). Garmin said 104F.

It seemed OK. Hot but OK. Emptied a water bottle in the 9 miles, 35minute trip.

My wife gets nervous when I'm riding over 95 F, but so far I haven't found any temperature too uncomfortable for my 9.5 mile (each way) commute. It helps that Sacramento has the dry heat. I'm not sure I'd try the same rides if I was still living in Kansas City.

I feel I should qualify my previous post.
Flats = no practical limit, maybe 120F.
Hills = 95F. Too much effort being expended to stay cool, for me at least.

Doesn't ever get too hot in Denver. I would say, practically, 100F.

In the neighborhood of one million degrees.

Thought the folks in the warmer climates might get a kick out of this...the picture below was taken yesterday (June 4, 2011) while on a brevet. Yes, that's snow. In June. Doesn't happen often, but it does happen.



Suffice to say, it never gets too hot to ride around here.

Just now in the shade of the front porch.

I hate riding in hot temperature but I rather ride the bike no matter how hot it is. So no limits for me.

I really feel for you. It's just started getting warm here after a very long winter. I think most of us are so sick of cold and damp that the few hot and humid days we've had nobody's complained. I saw a ton of bikes out on Friday when it was 90 and humid vs. the week before when it was wet and barely 60.

Thought this thread was about ladies cycling attire??

For me hydration starts getting serious at about 80 degrees and the more so on a pretty steep curve as the temp goes up from there.
Never ridden in temps over 100. It seems like pulling hard on long uphills in temps like that is asking for a heatstroke.

I won't usually ride when temperatures are higher than about 75 ~ 80 degrees, as I'm sensitive to heat.

I didn't use to be so sensitive to heat, but since my near "collapse" a few years ago, I've become sensitive to heat. In warm/hot weather I now have to take things easy and make sure I'm well hydrated.

Speak for yourself. I much prefer 50s and 60s to what we had Friday and Saturday. It may be just because it warmed up so quickly that I haven't had a chance to get used to it, but the last 20 miles of a 70 mile ride took me almost 4 hours including rest stops.

After two weeks of riding in 90+ temperatures, it's definitely getting easier for me. Becoming acclimated to the heat and humidity is the key, and commuting is a great way to do it because you have a relatively cool (altho humid) ride in the morning and heat in the afternoon. Yesterday I rode a century with temperatures near 90 F the last couple of hours, and it didn't feel too bad at all. However, if I hadn't been commuting nearly every day in the heat, I would have suffered.

I doubt many of the people I saw on Friday were doing anything close to 70 miles, - probably much less than 7.

I like wintery weather in the winter and summery weather in the summer. To me Saturday was about ideal, - mid to upper 80's. It might have been a tad humid but nothing awful. I grew up living on a lake and if it was much under 80, it could put a damper on the fun that could be had in the water.

Rochester is sometimes a few degrees hotter than Minneapolis though.

To be fair, that cold weather was a glitch; we've had some beautiful warm days, also after a too-long winter. It hasn't broken 80F yet this year, but we'll get there. Eventually. Maybe. We'll hit 90F for a day or two most years, 100F is as rare as snow in June.

Since today it was about 97, I decided to take a way home that's popular with both commuters and recreational cyclists to see if the heat had thinned the herd any The last time I had taken this way home was Thursday and the weather was pretty nice from what I remember.

At first I didn't think it had made much difference. There was a steady stream of cyclists. I went by 150 before I quit counting. There were runners (one guy with a big pack) and skaters along with people just walking. But when I got to what's normally a pretty busy section, it was clear that there weren't as many. I'm sure the weather was at least part of it, but I did leave work a bit later than usual too and maybe there's just not as much going on a Monday night.

Still nobody seemed to be really struggling or uncomfortable. The humidity had been dropping as the temp rose so IMO it really wasn't bad. Tomorrow is supposed to be both warmer and more humid so we'll see.

I also encountered something very sobering. Just I was turning off the trail I saw two police cars inside a taped off section of the street. Also inside the tape was a minivan with a crumpled bike behind it. What appeared to be the driver of the van was there but no cyclist in sight. The cops were making marks in the road. It didn't look good. If I had to guess I'd say the van hit a cyclist in the crosswalk but I can't say for sure. Just a reminder that while you have to take the heat seriously, it's not the biggest danger we face.

On another note, elsewhere in town some pavement had buckled due to the heat. This was on a major intestate blocking 4 to 5 lanes and creating major traffic jams, - so those who chose to drive instead of ride might have been wishing they hadn't.

Just an update. I found some info on the accident on a local cycling board. Here's a picture that looks like it was taken awhile after I had gone by since there's only one cop car. I guess there had been as many as four. Someone had seen the paramedics and the cyclist but couldn't tell how he was other than there was a lot of blood.

So far, 120 degrees F is the hottest I've ridden in. Haven't found my limit yet.