Temperature during daytime seems several degrees too low

Just curious, but I’ve been noticing since being online that my daily temperatures have been several degrees lower than surrounding temperature sensors, for both highs and daytime temperatures when there is sunshine. Nighttime temperatures seem to be pretty close to everyone else. My station is positioned correction in full sun during the majority of the day.

I noticed the same thing, since I happened to install a new Tempest in the middle of a heat wave. The UV index values were obviously way off also (like 6.0 instead of 11+). It looks like the UV indexes got themselves successfully calibrated about a week after installation. Not sure about the daytime high temperatures as of yet.

This is what I’m seeing still, that’s making me doubt things in a Weather Underground map comparison around the hottest part of the day. My station’s own hourly forecast shows up to five degrees warmer during the day. Installation was a week and a half ago, and I don’t know what all else needs time to get calibrated other than the super obvious UV Index correction that’s already been made. Just like the OP, in the evening my reported temperatures look to be much more in line with others nearby (as well as its own hourly forecast).


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I personally wouldn’t use WU has a guide. Use MesoWest and only use NWS & RAWS stations. CL doesn’t calibrate temps. Elevation and geographical features play a big role in the temps.

Not directly but it is used on SR & UV which then used on the Tempest to calculate a correction to temperature in sun with little to no wind.


that’s true, the unit warms up because it is in the sun, but because it measures how much sun it receives it can compensate for it. I think I found your station, or at least a station with an obvious UV calibration. It doesn’t show any calibration done to the Solar Radiation values.
(i’ll make a separate post about that because I think this is curious)
Now UV radiation probably don’t heat up the the unit that much. Solar Radiation is more important, so I hope that weatherflow is using that value to correct for the reported temperature. Perhaps your solar radiation values should also be scaled down. Now it thinks it sees more sun than it does, and therefore thinks it heated up more and corrects the temperature accordingly.

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I called the UV Index calibration “super obvious” because it was recording no higher than 6.4 on one (extremely hot and sunny) day and then up to 13.4 a couple (still extremely hot and sunny) days later. I did not see a similar change in the brightness or solar radiation values.

But that’s definitely why I was wondering if there are more calibrations yet to come, since the way it’s been recording temperatures during the hottest and sunniest part of the day feels like it may be overcorrecting in its calculation for how much the unit has heated up during the day.