How hot should a sauna be?
The short answer: about 70–90 °C (160–195 °F) on the thermometer, with dry air between the ladles of water. But the number on the wall tells only half the story. Where the thermometer hangs and how much löyly you throw change the feel more than a few degrees do.
What heater makers such as Harvia suggest for a home sauna.
The range Finnish researchers give at the bather's head level.
Typical between throws of water. Löyly raises it for a moment.
Why the numbers differ
Hot air rises, so a sauna has layers: the ceiling is the hottest, the floor the coolest. A thermometer near the ceiling reads higher than one at the level of your head on the bench, and the bench below reads lower again. That is why one source says 70 °C and another 90 °C for the same feeling.
Hang the thermometer on the bench side, at about head height when you sit on the upper bench, and away from the heater. Then it shows what you actually feel. In a well-built sauna the difference between your head and your feet is small; if your feet are cold while your face burns, the benches are too low or the ventilation is off. What makes a good sauna →
Temperature and löyly work together
Dry heat and humid heat feel very different. A ladle of water on the stones sends a wave of steam through the room: the humidity jumps for a moment, and the same air suddenly feels much hotter on your skin. A Finnish sauna is about that interplay, not about the highest number.
- Lower temperature, more löyly. Around 65–75 °C with regular throws of water gives soft, moist heat. Many Finns prefer this, and it suits beginners.
- Higher temperature, less water. At 90 °C and above, small throws are enough, and big ones sting.
- Very high and very wet is not the goal. Endurance contests ended in Finland after a death in 2010. A good sauna feels soft and even, not punishing. Sauna myths →
A rough guide by feel
| Thermometer | How it usually feels |
|---|---|
| 60 °C · 140 °F | Mild. Long, easy sessions; a good start for beginners and children with adults. |
| 70 °C · 158 °F | Comfortable. Plenty of room for löyly. |
| 80 °C · 176 °F | Classic home sauna heat. Löyly is strong but pleasant. |
| 90 °C · 194 °F | Hot. Short sessions and small ladles of water. |
| 100 °C · 212 °F | Very hot. Mostly for experienced bathers, with little water. |
How it feels depends on the thermometer position, ventilation and the person. Listen to your body rather than the number.
"Dry sauna" and the American rules
Many gyms in the US post "dry sauna, no water" signs. It is usually not because the heater cannot take it: most heaters with stones are designed for water, and gyms ban it for their own reasons. A Finnish sauna is meant to have water thrown on the stones: the heater is designed for it, and the steam is the point. In a home sauna with a proper heater, use the ladle. Why gyms say no, and how to throw löyly safely →
If your sauna won't get hot
- The heater is too small for the room, especially with glass, stone or log walls. Check the size.
- The stones are old and packed tight, so air cannot flow through the heater. Sauna stones guide.
- Too much ventilation during warm-up, or a door that leaks. Ventilation.
- Cold surroundings. An outdoor sauna in winter needs longer to warm up. See warm-up and cost.
Stay safe
Leave when you feel dizzy or uncomfortable, drink water between rounds, and skip the sauna after alcohol. If you have a heart condition, low or high blood pressure, or are pregnant, ask your doctor what is right for you. What the research shows →
Sources: Laukkanen, Laukkanen and Kunutsor, Cardiovascular and other health benefits of sauna bathing, Mayo Clinic Proceedings 2018 (80–100 °C at head level, 10–20 % humidity); Harvia heater operating instructions (65–80 °C).