Need Sauna High-temp Thermometer/Humidity Sensor

I am looking for a good temperature and humidity sensor that can keep track of my outdoor sauna.

I have a wood-fired sauna in the woods I built last year, and would like to keep track of temperature gradient while it heats up so I know when to reload wood as well know when it is ready to head in. The only power I have out there is two POE+ ethernet cables, one with a transformer to 12V to power the installed lights and the other attached to a 4 port POE switch to power a Unifi AC repeater and Reolink camera for wildlife viewing. I do have access to wifi and POE ethernet, 12V connection, and 5V connection that is attached to my boat-style light switch, so options are available.

Requirements would be a temp sensor that would handle at least >80C (180F), and below <0C (32F) would be a bonus. Can’t seem to find one on the market that has this temperature tolerance.

I have found a temp sensor through Adafruit that could do this (and more) I think I can add to ESP32 and could be a good first project for me to use ESPHome, but I would need to figure out how to power it and then install a screen to view while in the sauna. And then there is always the problem of finding the time to build it…

Anyone have any ideas for “plug and play” addition to HA?

As far as the Adafruit sensor for ESP32 build/integration I was looking at the following:


I still wouldn’t have the next step if I go this direction, including which board t set it up to. I do have a RPi 4 with POE hat that isn’t being used, but feel it might be a bit overkill for this application.

I am using Ruuvitag BLE sensor in Sauna. Ruuvitag pro sensor has a temperature range from -40 to +85C.

In Sauna hottest temperature is near roof, so another opition is to install sensors lower and calculate “offset” to real temperature

Thanks for the recommendation, that could work for my purpose.

Which Integration do you use and what do you use to connect the Bluetooth to HA? I will have to find a hub to connect it out there as it’s no where close to any other sensor I have.

I have Ruuvi-gateway that connects to BLE sensors and sends data to MQTT broker in HA server. Node-red is then used to process data for HA. I found the integration from Ruuvi community.
You can also build your own GW using RPi, SW is freely available. There is also direct BLE integration for HA, but range might be more limited.

Hi Amppa,

I’m totally new to Home Assistant. I have a Ruuvi Gateway and a Ruuvitag Pro. I’m not a python programmer but would love to use them with Home Assistant.

Is it possible for you to guide me to set this up? I already installed pyscript in HA. This is where I am stuck at.

Many thanks.

I would use an ESP32 programmed with ESPHome. You can get Ethernet versions, with or without PoE.

Look into these and choose the one that best suits your operating environment:

Choose a screen:

Maybe this?

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Yes, ESP32 is very nice and easy to integrate into Home Assistant but it has limited Bluetooth range. I would like to use the Ruuvi Gateway which offers superior Bluetooth range. I already have this and a Ruuvitag Pro. The Ruuvitag Pro sensor is waterproof and it’s quite robust.

Thanks for the suggestion.

I was not replying to you, I was replying to the person who created this post. They said they have wifi and Ethernet in the sauna, so the ESP32 solution I suggested would work for them.

You should start your own question in a brand new post if you are expecting answers specific to your problem.

Hi gcshum,

I am using intgration via MQTT and Node-red. See GitHub - oiv/ruuvigw_node-red_ha: Ruuvi gateway to home-assistant using mqtt


Hi @taylorlightfoot - I actually pulled the trigger and went full on with ESPHome. I like it, and even with the extra components I bought, it came way cheaper than any Bluetooth solution.

TTGO T display

This was a nice option since it had a tiny OLED screen attached.


I also went a little deeper and got the more advanced sensor. It is classed to go to sauna temps and has humidity with air quality so I can see if any smoke somehow builds up in the sauna. It’s a sealed system with the fire door to the stove on the outside, but sometimes downdrafts are wired.

POE 12V converter

There seems to be only 1 real ESP32 POE on the market, it’s expensive, hard to come by, and the dc/dc converter gets hot some say. This kit seems to be the better option, and I can hide it all behind the cedar. Right now I only have it hanging on the wall.

The plan is to carve the OLED as a window in the wall, should help protect it from the heat a bit. The Wi-Fi connects great and everything worked great for a while, but I do need to calibrate the sensor at higher temps. It’s about 15F lower than my analog thermometer.

The other issue is it will hang after a while, at random. Needs a full power reset to reactivate for a time. I need to pull it back in and double check the board for any issues and check through my code. I based mine off of someone else’s TTGO code and adapted to read the BMS680, but work has been busy so I can’t look at it for another or so.

Thanks for the tips though, ESPHome is pretty powerful. Not having to relearn python or arduino and coding with just bits of YAML makes me feel I have superpowers.

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I like ESPHome a lot, I’m glad its looking promising for your needs. I try to use it when I need something custom, it’s usually the cheapest option with the most flexibility. I use it to controls relays for HVAC system and for skylight controls and for button press inputs. I also like to use it for recessed door contact sensors and status lights. I made a custom closet light control for someone where the door sensor turns the light on while the door is open. Works well even as a standalone solution without Homeassistant.

There are so many ideas for these little things. My next project after I get the sauna temp stable is to make a weather-proof one for the greenhouse and have it let me know when I have to open the door after it gets too hot. Also like the idea of a duel temp sensor for the refrigerator/freezer - I hate French doors that I always seem to find open from my significant other.

I have thought about making something for our geothermal HVAC controller, but a little timid to mess with it that much. Need to have that be rock solid, and sometimes dumb manual controllers are still best. I don’t really need to make a schedule since that kills the efficiency of heat pumps. For now I’ll make a few thermostats and air quality sensors before entering into the relay game.

Hi Amppa,

Thanks for the link. I have followed the instructions and I can listen for ruuvi/# messages coming in using the MQTT broker. However, I do not see anything appearing under the MQTT integration. Thus, I cannot see the Ruuvitag sensor information when I try to put it on Lovelace card.

Any suggestion?

Check the “Listen to a topic” under MQTT integration. Put # in “Topic to subscribe to” and press “Listen”. You should see the messages. I get like

Message 140 received on ruuvi/FB:70:0A:4D:B1:06/D9:2B:34:64:F2:AA at 20:12:

“gw_mac”: “FB:70:0A:4D:B1:06”,
“rssi”: -70,
“aoa”: [],
“gwts”: “1649005959”,
“ts”: “1649005959”,
“data”: “0201061BFF99040517EB1AC2FFFF03A4FE44FFF8B3D667EF4BD92B3464F2AA”,
“coords”: “”

If you are not seeing the messages, put you see them in your MQTT broker, check if MQTT intgration is working.

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Hi Amppa,

I made a silly mistake of putting ruuvi/# for the topic in “send to ha” node. After removing that, it worked!


One year later, same question as the thread starter, so are there any new recommendations?

When going through the links above and digging further, it seems like SHT3x-DIS is great for sauna use at it is specified up to 125°C, correct? What would be the easiest way to connect one of those to an Ethernet port and use it in HA?

I am just finishing my sauna and I was faced with the same quandary. I was considering using and esp32 and a couple of different probes when I found this Shelly unit.

I will see how it goes

I would think twice about the Shelly temp sensor. The screen and housing doesn’t look like it is up to the task of high-heat situations. I tried a PP and PE cover for one of my probes and while it didn’t melt, it significantly deformed in the heat, IR, and air flow. Unprotected screens in direct heat I find won’t last.

What I am currently using is a Govee grill thermometer probe, although since it’s freaking Govee I still can’t figure out how to connect it to HA… AARGH!

It has a magnet on the back to hang from a grille, so I just pushed a screw next to my candle window in the changing room and pushed the probe through a drilled hole into the sauna so only the pointy tip is showing about 0.5 meters down from the ceiling. It works perfectly, and I can have 3 other probes to get floor temperature and changing room temperature. My sauna is outside, but unfortunately since it’s a thermistor it won’t go below freezing.

Really, it is perfect for so much of it - I just wish I could connect it to HA. It has both wifi and BLE, but I can’t seem to sniff it out with ESPHome.

Weird mentioning that the housing of the Shelly might not survive the heat. If the temperature can take up to 120 degrees how could it do that in complete isolation of the housing?