Hot commute

At what temperature does it become dangerous to try cycling in? I commute to work, 11 miles each way, and my shift starts a 4am, so the ride in to work is nice and cool. But I get off at 2:30pm, which is the hottest part of the day. Today, it was 95 with a heat index of 101 and 44% humidity. From what I hear, tomorrow is supposed to be a scorcher, 97 with heat index of 107. I don't push too hard on the ride home and haven't had any problems yet, but I don't want to end up in trouble because of the heat. I would rather take the motorcycle in and not risk the heat-related problems and just catch a ride in the evening when it cools off. But if these temperatures are routinely faced by cyclists and they have no problems, I will continue riding as planned.

Hey, you might be interested in this similar thread I started during the last big heat wave around here.
http://www.cyclingforums.com/t355592.html

The upshot of the replies were - heat is OK as long as you keep hydrated and pay attention to cues from your body. Personally I stop having fun above 100F. I'd also make sure that the air quality is OK - I think that is probably just as / more dangerous than the heat.

Agreed, the hottest I've ridden in so far is 110F heat index full sun & 10lb backpack. Just riding from work (10miles). It wasn't really bad unless I had to stop for lights or other traffic, then it was almost unbearable. If it wasn't for the "conditioning" aspect, I wouldn't have ridden at all.

Stay hydrated and watch your heart rate. Stay moving (at any speed) if at all possible as the wind helps you stay cooler (even if it feels like a suana)

I take an extra bottle of ice water just to squirt onto my head and neck when I start to get really hot. It really helps on the leg home at the end of the day when the temps get stupid high. And yeah, the stops with no wind are the worst part.

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I was on the SAGBRAW ride in WI a couple weeks ago and the first day was a brutal 68 miles with a 110 degree heat index, based on an air temp of 95. One of the guys on a bent was recording a 111 air temp on the road so I don't know how high the heat index really got. We survived by stopping quite often (5-10 miles) in the shade to cool the core body temp and splashing any water on you that you could. I know at least one rider was hospitalized because they couldn't get his body core temp down.
Just make sure you drink steadily even after the ride too. We had someone get severe cramps well after riding because he didn't keep rehydrating after we stopped.