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Mysterious Temperature Spike 2

I saw another mysterious temperature spike in the temperature sensors in my apartment! Here's what I saw when I checked my Home Assistant dashboard while out of town in November:


What's different between these two spikes and the last time I looked into this effect is that I now have two temperature and humidity sensors. They're both in the same room, with one sensor on the west wall of the room and one on the east side. There's also a large window facing south that I get a lot of sun through. This setup happens to provide perfect conditions

What's going on here is the same thing I posited in the other temperature spike note: sunlight is falling on a temperature/humidity sensor and causing the temperature to go up and reported humidity to go down! The double spike is extra fun because I see the sunlight effect twice: once in the morning, when light coming in from east warms up the thermometer on the west wall, and again the afternoon when the sun setting in the west illuminates the sensor on the east wall.


Quick sketch of the temperature sensors (#1 is blue, #2 is purple) in relation to sun and south-facing window.

This setup rules out that the room's actual temperature and humidity changed that much during the day. The temperature and humidity can change quite a lot if I open windows, take a shower, or boil a pot of water on the stove. However, in those cases, I'd expect to see both temperatures and both humidities all rise and fall together. The two distinct bumps at different times throughout the day I see in this lastest graph suggest that the room temp and humidity isn't changing very much, but the the sun shining on these sensors at certain times of day is influencing their reported readings quite a bit.

This was a very fun natural experiment that I was lucky to catch when I check the temperature and humidity curves for my apartment while I was out of town!

20/11/2023 15:13