How do skin blood vessels respond to hot weather?

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Claude Bernard Claude Bernard, detail of a lithograph by A. Laemlein, 1858.

In hot weather, the blood vessels in the skin expand (dilate) to dissipate excess heat from the body. This process is controlled by the vasomotor nerves, which regulate the diameter of these vessels in response to environmental temperature changes.1

By allowing more blood to circulate near the skin surface, the body can effectively release heat into the external environment. This mechanism is a key component of homeostasis, the process by which the body maintains a stable internal environment despite changing external conditions. The French scientist Claude Bernard was instrumental in explaining this regulation of the blood supply, demonstrating how the body maintains thermal balance through these vascular adjustments.231