UV seems too high or too low (solved with auto-calibration CL system)



My UV is reporting too high.
It’s at 9.3 right now. Yesterday I have seen numbers >10
We barely get max 8.1 if I am not mistaken.
Can this be calibrated?



Great product, everything went fine, shipment, payment, install.

Yes thats definitely too high we should have a code red alert when this happens in NL , but 20 C teperature is also too hight atm furthermore this staion in The Netherlands is also reporting too high https://smartweather.weatherflow.com/share/2185/graph/10302/uv/2 as you said 8+ is very uncommen over here

added a link of UV in the middle of the Netherlands by RIVM https://www.rivm.nl/Onderwerpen/Z/Zonkracht

I am aware the temperature is reading higher.
My Air is not situated on a perfect spot yet.
No problem with the temperaturesensor expected.

From the link, I see max UV today was around 7.

UV 8 and higher sometimes happens in The Netherlands. But verry uncommon.
Between 7 and 8 around the longest day is often achieved.
Looks normal to me in the graph.

i see much higher 10.2 > might have to familiarise with the app display or web display way to too high for that latitude


That is indeed way to high. Strange… Some users also have to low UV index.
Can it be calibrated?

i dont know but i observed many uk stations yesterday with similar high UV readings and being from the UK i know that they are far far too high perhaps weatherflow staff will diagnose and address the anomaly.

i never observed any high readings consistently with uv in field testing however i did momentarily observe occasional cloud reflection effect but nothing prolonged and regular and as high as what i have ben seeing from the newer stations coming online this week …

uv was max 7+ and uv isnt always highest on the longest day in may you can expect 7 too on 54 degrees lattitude above 8 is exceptional so there is definitly something wrong hopefully weatherflow will jump in.

Indeed. But the most high UV readingd are in May juni and Juli…
Hopefully Weatherflow will come with a solution. Still waiting on the whole package.
Maybe they used other UV reading sensors?

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was there some clouds near the sun?
as they can reflect the sunlight so that you get 2 bites of the same pie

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i think something is seriously wrong take a look at this chart from holland station .



Installed mine this evening, let’s see how the measurements will be.

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I too seem to have much higher UV index readings. Here in the U.K. I shouldn’t be experiencing 8 but am getting 8.5.
I know we are just past the summer solstice but the readings do seem high. There is high thin cloud so could this be due to UV bounce?

I have seen readings of 8 reported by other weather station types in the UK over the last week
so a reading of 8 is OK in the UK that you were getting

Not sure about today, but following the metoffice link, there are plenty of 9’s forecast for tomorrow as well, so 8.5 isn’t out of the question:


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First of all I like to say that I am very dissapointed.
My question about my UV is up now for 12 days and not a single response from the WeatherFlow Staff.
Since this is an official WeatherFlow forum and the UV readings problem is widespread and we are talking about a shipped finished product and the fact that it was extensively tested and calibrated reading from the indiego updates, this is really bad advertising.

Second, we got some very pretty weather the last ten days.
Clear blue skies across the whole country.
For 3 days, I monitored all 23 stations present in the Netherlands and it was shocking to see what readings that UV sensor produced.
From extremely low to extremely high and in between.

I don’t know how these stations are situated.
I watched their UV graph and noted the highest value for that day.
I will start with the stations discussed here in this thread, later I will post results from the other stations.

The RIVM website is an official website from our government that is monitoring UV amongst others.
Information from their website about UV:

The highest UV can be expected 4 or 5 days after midsummer (21-06).
About 4 days in a year the UV will be more then 7.
In the last eleven years, we have had only 2 days with the UV greater then 8.
In midwinter the UV is smaller then 0.5

Monitoring days June 29 and 30 and Juli 1.

RIVM measured (gemeten): 6.9 - 6.8 - 6.9
My station id 2254: 8.7 - 8.5 - 8.6
fransbrus station id 2172: 10.7 - 11.1 - 11.0
holland station id 2167: 13.7 - 12.9 - 13.2

** The holland station is now situated in Belgium and is still reporting extreme high numbers.
UV numbers in Belgium compare to those in The Netherlands though.

More numers of my station id 2254
29/06 8.7
30/06 8.5
01/07 8.6
02/07 9.2
03/07 8.6
04/07 8.6
05/07 8.7
06/07 Today mixed with clouds and clear blue sky, maxed out at 9.7 at 1 pm.

Other stations that reported a UV number far too high over those 3 days.

id 2161: 11.3 - 11.5 - 11.6
id 4173: Unknown - 11.2 - 11.7
id 3065: Unknown - 10.2 - 10.6
id 2176: 11.3 - 9.7 - 9.8

I may have missed or overlooked some stations in The Netherlands.
If you are from The Netherlands and your station is reporting a much too high UV number please respond to this thread.

I’d like to ask the WeatherFlow Staff to take a look at these stations discussed here
and fix those numbers.

I will report numbers over 3 days for the 23 stations available those days in a follow up.

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I’dont have the station yet but I’ve followed it too it seems you can feedback if your are readings too low anyhow look at this for the whole year 2016 the UV scale doesnt reach higher as 8 for the middle of The Netherlands input

A good source for UV forecasts is over here input longitude and latitude http://www.temis.nl/uvradiation/nrt/uvindex.php?lon=6.0006&lat=52.22

Hello your not wrong I have been following many UK stations and one station in holland for a few weeks

perhaps just been missed or overlooked by the staff I would advise to contact them direct .

I tested for UV for many months here in istanbul we get a much average higher than you guys at that latitude .I never once had seen extreme values in fact the early sky model was known to be extremely low on readings (under reading) and was improved in the later models with a better component. There is some obvious factory error calibration going on here .

i just looked at station 2167 and thats just an outrageous reading of 14.3 .

strongly suggest you get in touch with them direct.



re field testing…problem is, there has been different batch runs of sensors used etc (compared to what the field testers had (and there was some in Europe)
and so it might be that the batch run used for Europe (which has different radio frequency) the factory calibration is not correct (as noted above)
its something WF should be able to fix via firmware updates hopefully

I have a pre prod and prod Sky in France, they were a bit off but generally ok, and since they are in calibration cycle, they are pretty identical though different hardware I think.