If 110°F or over was predicted, I don't think I'd go out. On one ride I do almost every year, it's twice been 105° at the bottom of the last pass climb at about mile 100. Those rides went fine. Almost all of that 2400' climb is in the direct sun, with a long switchback near the top next to a dark rock wall about 6' away. The last time it was that hot, they sagged about 100 riders off the course. One of those years we were on our tandem and thus really slow. Starting that last climb there was a young fit looking guy in front of us dressed all in "cool black" to his wrists and ankles. He was riding no hands, arms held straight out at his sides, barely managing our pace. He pulled over pretty soon and I assume was sagged off. Cool black is not, no matter how cool it looks.
That was one of our most memorable tandem rides, though. The last 30 miles were cooler and upwind and we were passing young guys on singles. We had a great time.
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