I'm doing the opposite of trying to beat the heat. June is usually my transition month for heat adaptation. Typically, including this month, we'll have mostly cool or just pleasantly warm days in April-June, then suddenly it'll get hot, with little transition.
Sure 'nuff, both of my 35-45 mile road bike rides with a group this week have been on the hottest days of the year, with temps jumping from 60-70 last week to 90s this week, with heat index peaking over 110F.
On Tuesday evening I was doing fine until the 30 mile mark. Then I noticed on the turnaround after a brief rest, I wasn't sweating. Bad sign. I slowed down, chugged more water with electroytes and a gel with caffeine. I was just starting to feel dizzy and headachy. And by the time I got home after 45 miles my head was throbbing -- in part due to a sudden barometric pressure drop before a t-storm that night.
On Thursday it was so dang hot four of us split from the regular group and took a slow and easy piddle pedal. One fellow still was on the verge of heat exhaustion. Temp index was 111F. We stopped for an hour to cool off before heading back.
By July I'll be heat adapted and able to ride pretty hard midday. But June is always tough. The trick is to recognize the warning signs and ease up. Sometimes just 5% lower effort is enough to get through a rough ride.