Heat wave

We have entered the ice-melt stage of winter (or is it spring, now?), and with temperatures soaring into the low 40s (F), Minnesotans begin to shed clothing.

Torsos bared to the wind, young Minnesotans revel in the warmth of a 42 F day.

Torsos bared to the wind, young Minnesotans revel in the warmth of a 42 F day.  I notice they are still wearing their warm running tights, though, as they cruise down the Mississippi River Boulevard.    (This is “drive-by” photo shooting, with one hand on the steering wheel and one on the camera shutter.)

The weatherman commented today:  “Isn’t it strange that 40 F in October feels so cold, yet 40 F in March feels so warm — why is that?”

This is a result of seasonal acclimatization, and almost every animal experiences it in response to long-term exposure to a particular climate.

In October, at the end of the summer’s dog days, we humans are still in heat dissipation mode, flushing heat to the skin to unload it and trimming metabolic furnaces back to reduce heat production.  With acclimatization to heat, we lack protection against the chilling effects of 40 F temperatures.

However, after a prolonged spell of exposure to freezing temperatures, we have revved up the metabolic furnace considerably to keep us warm (the thyroid gland plays an important role here), and the blood flows to all extremities via a central core of vessels (deep to the skin surface) to conserve heat.  Other warm-blooded animals would have added a thick layer of insulating body fat, fur, or feathers to protect them from losing heat.

So, it’s really no surprise that a day above freezing would be considered a heat wave.  It must be time for a picnic!

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