Saunas Build Heat Tolerance in Days, Won't Cool You Mid-Heatwave
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- UK Health Security Agency has issued heat-health alerts across much of England as parts of the UK experience their fourth heatwave of the year, following what the source calls an "unprecedented summer" in which western Europe recorded its hottest June on record.
- Prof Jari Laukkanen of the University of Eastern Finland says repeated heat exposure produces well-established physiological adaptations — earlier and more efficient sweating, improved skin blood flow, expanded plasma volume and reduced cardiovascular strain during subsequent heat exposure.
- Dr Jessica Mee of the University of Worcester is recruiting participants for a study on whether regular hot water immersion improves the body's heat response, and notes people accustomed to heat pace themselves more sensibly, hydrate more consistently and recognise warning signs earlier.
- Heat training typically requires 40–60 minutes of daily exposure for at least four to six days, with benefits lasting about a week — though longer training extends the effect, according to the experts cited.
- Dr Heather Massey of the University of Portsmouth cautions that the adaptations rely heavily on the body's ability to increase sweating and skin blood flow, meaning heat acclimation benefits may not be equal for everyone.
- Laukkanen stressed heat adaptation "is not the same as heat protection," with limited evidence that sauna use during a heatwave itself protects against heat-related illness; Mee warned that stacking thermal challenges onto a body already dealing with poor sleep and dehydration creates the precise profile in which heat-related illness develops, with fainting the most immediate risk for unsupervised home use.
- Community Sauna Baths, a not-for-profit where Nicola Pegues is head of operations, initially saw bookings dip as temperatures rose but is now seeing them return; all of its sites are outdoors pairing saunas with cold plunges.
Why it matters: For people in England navigating repeated UKHSA heat-health alerts, the research points to a genuine long-term acclimation option — but both Laukkanen and Mee warn that using saunas as a midday cooldown during a heatwave can backfire, with fainting flagged as the most immediate risk for unsupervised home use.
