What temperature should a sauna be?

The short answer: 70–100°C for a traditional sauna, 45–60°C for infrared — and the two figures are not measuring the same thing.

Traditional saunas: 70–100°C

Finnish practice puts a traditional sauna somewhere between 70 and 100°C, with most people settling around 80–90°C.

That number is measured at head height on the top bench, which matters more than it sounds. A sauna stratifies strongly: the difference between floor level and ceiling can be 30–40°C. A thermometer mounted low, or near the door, will read dramatically cooler than what you actually experience sitting on the top bench.

Above 100°C, most people find the experience punishing rather than pleasant, and the risk of overheating climbs. Higher is not better. If you cannot stay in long enough to relax, the temperature is working against the purpose.

Infrared: 45–60°C, and not a weaker sauna

An infrared cabin runs at 45–60°C, and people new to them often assume that means a milder session.

It does not, because the mechanism is different. A traditional sauna heats the air and the air heats you. Infrared emits radiant heat that your skin absorbs directly, so you get a comparable sweat response at a much lower air temperature.

Comparing the two on thermometer readings is like comparing an oven to a grill on the same number. See infrared vs traditional sauna for how that plays out in practice, cost and installation.

Humidity changes everything

In a traditional sauna, throwing water on the stones — löyly — slightly lowers the air temperature while sharply raising humidity.

The perceived heat rises even as the thermometer dips. This is why two saunas at an identical 85°C can feel completely different, and why the temperature figure alone never tells the whole story.

Typical traditional sauna humidity sits around 10–20%, rising briefly with each ladle. A steam room, by contrast, runs near 100% humidity at 40–45°C — a genuinely different experience, covered in sauna vs steam room.

Heat-up time and what it costs

A traditional electric sauna typically needs 30–45 minutes to reach temperature. Wood-fired takes longer. An outdoor cabin in a Cornish February takes longer still, and a poorly insulated one may never comfortably get there at all.

Infrared is usable in 10–15 minutes, because there is no air volume to bring up first.

That heat-up time is most of the running cost — the heater draws full power throughout it. Insulation is what decides how long full draw lasts, which is why it shows up directly in the bill. See sauna running costs and sauna insulation.

Setting yours

• Start lower than you think. 70–75°C is a reasonable place to begin; work up as you find your tolerance.
• Put the thermometer at head height on the top bench, away from the heater.
• Let it stabilise. A sauna that has just hit temperature is not yet evenly heated — the benches and walls are still absorbing.
• Adjust with water, not the thermostat. Small amounts on the stones change the experience far more effectively than chasing another 5°C.
• Match the heater to the cabin. An undersized heater never reaches temperature in a cold outdoor cabin; an oversized one cycles and heats unevenly. Sauna sizes and occupancy covers the sizing.

The short version

• Traditional: 70–100°C, comfortably 80–90°C, measured at top-bench head height.
• Infrared: 45–60°C — different mechanism, not a weaker session.
• Humidity changes perceived heat more than the thermostat does.
• 30–45 min heat-up traditional, 10–15 min infrared.
• Higher is not better; the right temperature is the one you can stay in.

Sources: NHS — Heat exhaustion and heatstroke