Low uv readings?

I have checked my tempest for showdows obstructions etc. Currently I am showing a Uv of 5.4 the current reading coming from the station KCOE at the airport about 3 miles away is over 7. No clouds or obstructions on this perfectly clear day. Anyone else notice anything?

Is this a new installation? I have read that a new Tempest needs a few sunny days to calibrate itself for the UV, Brightness, and Solar Radiation parameters.


It has been up since the last week of June. It has had readings in the 9s on other days. The closest weatherwise roughly 10 miles via air is currently showing 9.7! Here are real time comparisos of our 2 stations. I see my uv is lower but my brightness and solar are higher. Am I

When I look back on your data it doesn’t look like there have been enough clear days around solar noon for the CL algorithm to determine that a calibration can be reliably made. Note that the days don’t have to be consecutive. It seems like it was 6-12 days needed or something similar.


Thanks will give it some more time and see how it goes.

So I have both production and Field test unit on same Hub 15465 And the production model is like 50% of the UV of the field test unit it has only been online for 2 days been really sunny and my 3 units Sky Tester and Production units are all in same sun on same pole at same height, from what I read you said it will take up to 7 + days to calibrate ? Sky Is 11.5 Tempest Tester is 11.3 And production Model is 6.4

I didn’t find the post right away which mentioned how many good days were needed which is why I gave a range. The solar noon time is mentioned here: https://community.weatherflow.com/t/uv-values-high-cause-sky-in-shade-at-solar-noon-throws-off-cl-calibration/3332/4?u=gizmoev


That Link did not work for me. Take a look at the 2 uv Brightness solar rad and/watts the one with lower UV has higher values of Brightness, radiation /watts ?

Logically, it is inside testers part but Gizmoev wanted to highlight this

…the UV calibration factor is computed from the highest observed value 30 minutes either side of solar noon (1 hour period centered on solar noon)

And if you have covered weather, shadow blocking at that period it will not validate the calibration and wait till another opportunity comes. Calibration routines run on average once a week though might be less these days with many new stations coming online.


Did you notice that the 6.7 had higher brightness and Rda/Watts values than the 12.2 UV reading

Also no shade here its cooking outside this week and all three of my WF devices are within a 3 foot circle with no shade from 10am to sunset I keep a eye on it and see when it does get the calibration applied


Sorry, I didn’t notice. :grimacing: Furthermore, I didn’t notice it was specifically not in the general Testers category.

I am still awaiting the calibration to take place with mine. I feel it is way off. At one point another weatherflow station near me had a uv of 11+ here is mine in the bright sun.

Still no improvement

I guess the other part of my question flew over everybody’s head why would the Brightness And the Solar Radiation be higher on the production tempest which has the 6.7 UV but reads 150212 lux on brightness and 1252 W/M2 on solar radiation
The Test Tempest read 12.2 UV and Solar brightness is 74120 lux And 618 W/M2 Solar radiation

I guess I also found a bug I tried to check to see if this was like this in the graphs but everytime I brought the pull down menu down to move the production tempest from card reading to Graph it would pull up the beta tempest graph graph will only display for my production tempest if I click on readings from card

The new unit may need calibration.

#1 Yea but look at the UV reading compare to Solar Brightness And Solar radiation then compare the Tempest test Unit and the production unit see anything fishy?

#2 I installed them both on same hub if you read the Information, the card reads correct for each unit but try switching to something in the graphs and not on card and it always pulls up Tempest test unit not Production unit Bug ?
David ( DSJ )Told someone hubs were Identical my hub has latest firmware 143

I’m guessing you installed the Test unit to the Hub first.

Yes its the beta test Hub dsj told someone on here that it was same and would be fine

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Here is where this was discussed


Ignore this post. I have no clue what the applications do. Haven’t looked at them in two years.

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That Kinda Su@@ I guess David ST John did not know that Did you notice the readings for the UV the 6.2 had higher readings than the 12.2 UV I know about the calibration but should the UV with the highest number also have higher Brightness and higher Solar Radiation you can see this in the picture I posted