Should I upgrade from Sky/Air to Tempest? (and related questions)

I bought my original Sky/Air Weatherflow in August 2019. Due to multiple problems, I am now on my third Sky unit. My current Sky unit and the second one both have the same problem where the wind sensor literally freezes up and stops reporting any wind data when the temperature gets colder than -20C. As I am now 4 months past my 2 year warranty, support is only offering a significant discount on a new Tempest unit. I am trying to decide if I just live with the wind sensor freezing up during cold spells, or if I should switch to the Tempest.

Has anyone experienced the wind sensor freezing up with the Tempest? My confidence level is not high for our cold Canadian winters!

Also, I currently have my Air mounted in a Stevenson box 5 feet above the ground. I feel I get very good accurate temperature reading with this setup. I am concerned about the accuracy of temperature reading with the tempest unit if it is mounting on my roof as my current Sky unit is. Has anyone upgraded and if so, have the Tempest temperature readings been accurate? I really have no other mounting options other than my roof for a good view of rain/wind/sun.

Any other upgrade experiences or thoughts in general would be appreciated.


Well … the Tempest does do some computations in sunny conditions to adjust the temperature a bit. But, depending on what your roof is made of and maybe some other factors, that may not be enough to give temperatures truly representative of your environment. You can continue running the Air unit even after deploying the Tempest and compare the readings, so, you can decide if you like the temperature readings you are getting from your Tempest. If not, you can continue running the Air as long as you like (I still run my old Air as an indoor sensor).

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WeatherFlow SKY and AIR were 2 seperate devices. Tempest° now integrates both of those two former devices into one device. You no longer have to place one in the shade (AIR) and the other somewhere else. Just place Tempest° in clear view of the sky and a clean wind fetch.

If your AIR device is still working more than half-way decently. . .you can place it indoors some where to measure room or basement conditions. . .that’s what I do.

I’d just live with the limitation and save myself the money.

Your Air+Sky have a lot of benefits over the Tempest:

  • both can run off AA so you don’t need to worry about the Tempest not charging enough
  • the Stevenson screen means your Air is optimally sited for temperature and no magic-math sleight of hand is required for accuracy. You can’t do that with a Tempest since it requires sun for power
  • the two-sensor setup means you can also optimally locate the Sky for wind (if it’s not frozen up of course)

That said, the Tempest has some improvements re: the anti-raindrop coating and the like, but I can’t speculate on whether that’s worth spending money to get, even if you got a nice discount on the upgrade.

If you upgrade, keep the Air+Sky running and use the (sheltered) Air for your temperature readings.


With the temps below -20°C here in Edmonton and have been for almost 2 weeks with the odd day above -20°C. I noticed my Tempest does not record wind very well despite being high enough to get wind. Under that temp the wind stays, below 5 km/h, even when official Environment Canada stations will say wind is 15-20 km/h. That is my only gripe about the Tempest, because everything else works great!


  • The ideal operating range is from -35C to 60C (-31F to 140F). At extremely cold temperatures, the ultrasonic anemometer may report wind speed readings lower than actual.
  • Temperature readings will be reported down to -37 C (-35 F). The device should not suffer any long term ill effects if outdoor temperatures drop below -35C (-31F).
  • The LTO battery used in the Tempest device will continue charging normally down to about -55C (-67F). At or below this temperature, the battery should be able to keep the device powered for long enough until the temperature warms up to allow the battery to recharge."

The temperatures in your Stevenson screen will be different to using a tempest above the roof for several reasons that I had never considered until Weatherflow staff told me and I experimented with.
Imagine an almost calm morning when the sun hits the wall of the stevenson screen. There will be a sunny warmer side and on the shady side the cold night will have chilled the wall of the stevenson screen which due to the calm air movement will have a delay warming up. Now depending which side of the stevenson screen the gentle breeze moves from, the temperature recorded by the air will either warm quicker or slower than actual surounding air temperature. The Tempest being in the sun suffers a similar issue and has compensation to correct the suns warming effect, and the actual air temperature at the Tempests location much higher above the ground will be different. Two thermometers in different locations especially in morning sun and shade will argue both the current temperature and the rate of change in temperature sometimes by a couple of degrees. The Tempest is quicker than my air in a stevenson screen to change. So prooving which temperature is more correct is very difficult.
I would leave your Air in the stevenson screen where conditions match what meteorologists would use at other weather stations and what you can relate your history to.
I would continue using your Sky as it is. I bought several skys because they were running out of stock and they have some advantages over the Tempest. I have a sky running several km from the hub.
I do not know your most important question about how the Tempest goes colder than -20.
The Sky battery system is not in the Tempest which is important if it ever runs without enough sun to charge the Tempest then the Tempest can run out of battery charge.
But when they solve the charging issue in dark installations then a new Tempest might mean you do not need to get up to your Sky to change its batteries if you had a Tempest instead. You could wait until they announce their solution to the charging issue and consider what they offer then.
Best of luck Ian :slight_smile:


Oh 100% it shows lower wind speeds or they get stuck. My station for example was between 4:30pm LT to 1:30 am LT, the lowest wind speed was 4.1 km/h, highest was 5.0 km/h. It also can get stuck in the wind direction. Right now wind is S-SE at official airports, my station says 273°-275° for The last ‘10 hours. So it’s unfortunate it happens when it gets to these cold temps. I still love my tempest regardless