Ice Bathing in Winter vs Summer – Is There Actually a Difference?

The Role of Air Temperature

The body begins its thermoregulation process before you even enter the water. In winter, when air temperature is near zero or below, the body is already in a mildly stressed state as you undress. Vasoconstriction in superficial blood vessels is partially already underway, and core body temperature is marginally lower than on a warm summer day.

This means the transition to cold water in winter involves a double stress factor – cold air followed by cold water. Research in thermophysiology shows that the combination of cold air and cold water produces a stronger noradrenaline response than cold water alone at warm ambient temperatures.

Water Temperature Is the Key – Not the Season

Here is the important point: it is the water temperature that governs the physiological effects, not the month of the year. A lake in July holding eight degrees produces essentially the same bodily reaction as the same lake in February at eight degrees.

The difference is that water temperature naturally varies with the season. Swedish inland lakes can reach 18 to 20 degrees in July – which technically does not even qualify as cold bathing from a physiological perspective – and drop below two degrees in February.

Adaptation and Seasonal Variation

An interesting aspect of regular cold bathing is that the body adapts. Research from Lund University and studies published in the Journal of Thermal Biology show that regular cold bathers develop a more efficient thermoregulatory capacity. The body learns to mobilise heat production faster and recover more effectively after cold exposure.

This means an experienced cold bather who swims year-round may actually find summer baths insufficiently challenging if the water temperature rises too much. Many then choose to supplement with artificially cooled baths or cold showers to maintain the stimulus.