We are in the midst of an unprecedented hot-weather spell, all over the intermountain west. Boise is supposed to have 5 or 6 100-plus degree days, before it settles back to more normal highs in the low 90s. (It's not too unusual to have a week of 100-plus days in the summer... but it's usually in late July or early August.)
Global warming? If so, it's not MY fault!
Does the extra 10 degrees make a difference? I'd say it definitely makes some difference. Cooling systems are put to the test on such days. We have a pet bunny - she lays still against a bottle full of thawing water, taking shallow breaths. Cars overheat. Our swamp cooler has been running nonstop for 3 or 4 days; sometimes I lie awake at night, worrying about it stopping. (There are a couple weeks each summer where it can't quite keep up, but most of the time it's adequate and significantly cheaper to operate than refrigerated air conditioning.)
Likewise, the human cooling system is put through its paces. It's really quite the amazing system. Blood circulates to the skin surface where it flows through capillaries. When it gets hot we sweat, and the evaporation cools the skin's surface. As the cooled-down blood continues its journey, it brings merciful relief to other components that would otherwise overheat. If it's not keeping up, the heart pumps harder, trying to circulate the blood a but faster. It's critical to stay hydrated, because that evaporating water is a very critical component.
On Saturday mid-afternoon I went on an errand-running ride of 80 or 90 minutes. I drank my water and filled it and drank it again... was starting to get quite uncomfortable. I stopped at a city park, drenched my t-shirt, poured a bottle of cool water over my head, drank a bottle's worth of water and refilled it... it was amazing how much better I felt as I rode away!
(As long as I have plenty of water to pour into the radiator, I'm good at 100+ degrees. Death Valley is pushing up on 130 degrees... that might be a little TOO much, for more than a few minutes.)
Stay hydrated, my friends!