98 degrees.... during a hot humid DC heat wave. It was probably 105+ on the blacktop though. 98 was the "in the shade" temp. We used up two liters of water in just 2 hours of riding. After that we were mostly in the shade and the sun started setting, so our water consumption went down. We were "bikepacking" along the C&O trail, so water wasn't exactly conveniently available.

The worst was not the heat, but actually the ozone-induced "lungburn" that we felt that night into the following morning. It was a feeling akin to asthma... lowered lung capacity, painful breathing, airway constriction, wheezing.