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


Morning. Two readings about 10-15 miles apart in my city (Sudbury, Ontario). His UV levels are at least twice as high as mine. For my northern latitude, his readings are wayyyyy too high (11 range).

Just sending these example for study. Looking forward to updates that improve other readings also. My lower readings first pic, his house higher readings 2nd pic.


Either that station is at a very high altitude, the location is incorrect or the sensor is faulty. That’s as high UV readings as we get here in Denver.

Is that Station 2211?

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This is definitely a calibration issue. We’re getting closer to adding a UV component to the network-wide continuous learning system, but it’s still only being applied to a limited beta group. I’ll add your station, along with the two others in Sudbury, to that group. Watch for those to improve soon.

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Thanks much. I know you’re all working hard there. Rome was not built in one day :).



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Yes his is station 2211. Mine is 3778. No high mountains in my area. Wish I had Denver mountains. :).

Max UV forecast for today was supposed to be 8, and that is not common. his sensor was better today or closer to mine anyway.

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Hi there,

I installed my new Sky last weekend. Unfortunately it’s not ideally sited, and doesn’t get direct sun until a couple of hours after sunrise. But it’s nicely exposed for most of the day.

I’m just wondering how long the calibration process should take.

In my area, the UV doesn’t get above 3 at this time of the year (late winter), yet my Sky is telling me it’s upwards of 12 in full sunlight middle of the day. (It rarely gets above 12 in summer.)

I’d have thought it might have sorted itself out by now.
Any ideas?

It can take a few cycles. The UV auto-calibration sub-system needs a set of data with clear skies for about an hour each side of solar noon. Looks like your system just updated recently.

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Hi David,

A follow up for the NZ stations that are in the beta group. Its looking pretty good! Maybe under predicting a little. We need to wait for higher UVI’s later in the year to really see.


A couple of stations don’t seem to be auto calibrating. 2594, 2620, 2593. They are excluded from the data. Maybe they were missed from the Beta group. Two new NZ stations 2589 and 4074 have popped up since last time too.

Compared to before calibration it’s amazing…

Take the data with a grain of salt, its using NIWA predicted data and I have no way of knowing the cloud cover condition at each station. It’s from different days over the last 10.

I’ll check again in a couple of months, the UVI should be up to 10 by then.

I was wondering if the app should have a UV warning (like it does for rain commencement)? I know you can do it via IFTTT. Determining a world wide warning level would be difficult as standards vary, AU/NZ its set at 3. US is 6. Maybe a user setting.


Thanks for the follow-up, Peter - great analysis!

Yes, we don’t have all stations in the self-calibration system yet, but we’re getting closer to a network-wide solution.

Indeed. Unlike rain start and lightning strike alerts, it would be tricky to create a UV alert that all users would want/need. A configurable alert may be better, perhaps in the future - we’re trying to keep the app super simple for now, and let third-party solutions (like IFTTT) handle the more complex stuff.

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It depends on where in US. I want to know when it’s above 10.



Our UV was very high for Green Bay, Wisconsin, peaking at 12.3. But the Sky just went online yesterday evening, and it was a very sunny day with blue skies – and in Wisconsin we aren’t used to seeing the sun, either – so I’m hoping this will calibrate.

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@miller.ted, do you want the SKY to calibrate… or Wisconsin to calibrate? The second may be a bit tough these days…


Could you take a look at my station? Number 4950

Maybe it’s to early because I had it up for just 2 days.
But when the sun peaks trough I have reading above 6.
For this time of year it is too high.
Normally would be around 5 or lower.

Sneek, The Netherlands

What is your altitude where you live?

I’m about 0.7 meters below sealevel.

I live in the Netherlands.

This in the sun callibration as far as I know mine goes up to 9.8 sometimes 5 could be highest on our latittude chek my station in profile or here https://smartweather.weatherflow.com/share/4967/grid lat about 52 N and long about 6

hey ron time to put the sun factor lotion 200 , max here for this time of year is 8 or there abouts much southerly latitude 41. than yourself just looked as yours dont worry it’s fixable…


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Hi Brian thanks for your advice I’m in the Vine cellar 10 meter under the ground I’m out of SPF 200 LOL

dont worry ron wait a few days if doesnt fall into the forecasted values then drop @dsj a message he is pretty responsive in dealing with UV issues . glad you finally got it … have fun…brian

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Ok will do and thanks