When the temperature climbs up after a cooler weekend, does the heat feel worse?

A: Yes, and the reason is not just psychological. Researchers know of at least three reasons.

First, the human body adjusts surprisingly quickly to temperature. However, this also means that after even one or two cooler days, you may lose a bit of heat adaptation as your blood vessels are less prepared to expand and you may sweat less readily. So then when the temperature jumps back to the mid-30s, the heat can feel more aggressive.

Second, humans perceive changes by comparison. A 35 C day after several 39 C days can seem manageable but after two 29-31 C days, it can seem oppressive. The reason is your nervous system is assessing the temperature according to the most recent baseline. This is also why lukewarm water can feel hot after you touch cold water.

Finally, you may be sensing changes in temperature as well as humidity. After cooler days, humidity, cloud cover, wind, and the overnight minimum temperature also often change. As a result, a still, humid 35 C after pleasant weather can strain your body more than a dry and breezy 37 C after pleasant weather.

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