WeatherFlow Smart Weather Station: Review

Home weather instruments have long been the province of weather buffs, with various levels of tracking and trending the usual weather data points simply out of interest. For smart home enthusiasts, the availability of external environmental data offers a great deal of practical use. From irrigation control to air-conditioner optimization, good quality local data sources can greatly help to make smarter automation decisions.

The availability of suitable instruments has been less than accessible for most home users, though. Expensive and often requiring custom integration to be able to use the data, it hasn’t really been a good match in the age of Alexa and IFTTT. That’s where weather services provider Weatherflow decided to step in when they crowdfunded a smart home weather station on IndieGoGo in 2016.

Hardware

What WeatherFlow came up with is a stylish and easy to deploy solid state weather station consisting of three parts; Sky, Air and Hub. The Sky unit is a sensor package that captures the exposed data points and is designed to be mounted on a mast of some kid. This is equivalent to the usual anemometer and rain gauge in typical weather stations. In this case, though, it also captures solar radiation, light intensity and UV rating. The wind and rain sensors are both solid state, using ultrasonic transducers and haptics respectively, instead of the usual mechanical solutions.

Left to Right: Sky, Hub, and Air

Left to Right: Sky, Hub, and Air

The Air unit is the under cover package used for capturing ambient conditions such as temperature, humidity, and air pressure. WeatherFlow also included a lightning sensor which can determine the presence of lightning within 40km and give an approximate range.

The Hub, as you would imagine, is the bit that connects the sensors to your home network and allows the smart portion of the name to happen. The reason the sensor packages don’t communicate with the WiFi network directly is to conserve battery life as the sensor packages are designed to run completely cord free. As such they use an industrial sub-GHz radio for telemetry back to the hub to provide greater range than WiFi at lower power cost. The quoted range for the sensor units is about 300m (1000ft), more than enough for most households no matter where you want to mount them.

The typical set up is to have the Hub connected to WiFi and communicating back to WeatherFlow’s servers. This is pretty standards for smart devices as it allows for the smartphone app to access the data from anywhere, and also allows you to share your weather data with others via a simple web page. You can access the sensor data locally using only Bluetooth LE, but then you are limited to only being able to access the data when connected to the hub, which severely limits the usefulness of the device by cutting off common integrations and notifications.

Since the release of the product, WeatherFlow has been working to improve the auto-calibration and continuous learning features built into the firmware. Initially there were various issues with sensor accuracy, with wind, rain and UV having various random results. These issues have been largely addressed with updates, and improvements continue to be made. Mileage appears to have varied between customers, and issues have not been consistent from device to device.

In my case, I’m pretty sure my UV rating is still over reported, with nearby official weather stations reporting lower on most occasions. Other than that, however, the data seems to be on the money bar a few minor issues resulting from the nature of the sensors being used. Two specific ones come to mind. The first being the lightning sensor. As it measures EMP to detect lightning activity, and needs to be fairly sensitive to function, it can be triggered by electrical switches nearby. WeatherFlow do note this in their installation guidelines, and it does seem limited to closely positioned electrical switches, so it’s certainly possible to keep it clear enough to avoid this. I have an outdoor smart switch nearby with regularly triggers a false positive, but as it’s only a single ‘strike’ it’s not a big deal.

The second issue pertains to the haptic rain sensor. This unit detects rain by measuring the impact of drops on the top of the Sky unit, and then using carefully calibrated calculations to determine the size and frequency of the drops, and thus the amount of rainfall. It’s stated to be accurate down to 0.2mm increments and does, indeed, work very well. The only case where it might be considered deficient is in the case of light drizzle. As the drizzle doesn’t create and impact, it doesn’t count as rain and won’t be measured, but this is also fairly minor in most cases.

Mounting the Sky and Air units is fairly straight forward. The Sky unit is designed to be pole mounted and includes a circular socket with a screw clamp on the base. Mounting is simply a matter of inserting the unit onto the top of a 1” pole and tightening the clamp. The device needs to be rotated North, and a mark is embossed into the plastic shell to facilitate this. This is to ensure wind direction is reported correctly. Note the pole needs to be correctly sized and securely mounted itself to provide a stable platform. Excessive wobble can cause sensor issues, such as false rain starts due to vibration.

The Air unit needs to be mounted in a sheltered location to ensure temperature and humidity reporting is accurate. As noted above, it also needs to be away from electrical sources to avoid lightning false positives. It can be placed away from buildings by installing it in a radiation shield if required. While a keyhole mount is provided on the base of the unit, WeatherFlow recommends mounting it vertically for optimum lightning detection and moisture drainage. To this end, a 1/4” thread mount is also provided. This was a perfect match for an old CCTV camera mount I had lying around, and made wall mounting easy.

Thread mount on an old CCTV arm

Thread mount on an old CCTV arm

Battery access

Battery access

Both the Air and Sky are powered by standard AA batteries accessed by twisting off the unit from it’s mounting base and opening the battery compartment door on the bottom. The Air takes 4 batteries, while the Sky needs 8. While the devices are designed for long battery life, the type of battery makes a big difference. WeatherFlow strongly recommends Energizer Ultimate Lithium due to their long life and high performance under a wide range of temperatures.

While this performance has proved worthwhile, with people generally reporting 6 months out of a set, those particular batteries don’t come cheap. In some places a set of 12 can cost around 30% of the price of the weather station. Other batteries have been reported to provide far less life, even as low as 2 weeks for regular alkaline. In my case, I’m still on my original set 6 months in, but the Sky is starting to show a mild voltage drop. This could indicate an impending failure as Lithium batteries tend to have a voltage ‘cliff’ where the voltage will remain fairly flat and then fall very rapidly at the end of their life. Still, 6 months is pretty impressive for AA batteries in any case given the unit is sending a wealth of data samples every minute, 24/7.

Software

As is typical with connected home devices, the software consists of a combination of a free smartphone app (for iOS and Android) and a back end service hosted by WeatherFlow. The service provides remote access to the weather data, notifications via the app, a personal webpage showing you weather data, and a web API that allows for custom integrations if you’re so inclined.

The app provides for simple setup of the weather station, guiding you through connecting the Hub to the your WiFi and then detecting the sensor units. The Sky and Air can be individually named, and you also need to provide a name for the location. This is useful if you have multiple weather stations in different locations, or course, and is also used if you choose to share your weather data page. This data can also be shared via Weather Underground if you have an account with them.

The web page essentially replicates the mobile app in terms of layout and functionality, (or perhaps it’s vice versa). The main page is a well presented list of weather data categories showing the current primary value, say temperature, and smaller supplementary values (humidity in this case). There are additional optional panels for battery level for each sensor unit. Each of these panels is clickable/tap-able which opens a graph view of the data value. The graph can be zoomed in to a 1 minute resolution, or all the way out to 1 day resolution which shows about a month worth of data on screen. This can be scrolled back, though, for a full years worth of data. Each data point can be selected to view the specific details for that point.

Example graph view (Wind)

Example graph view (Wind)

The units of measure are, of course, configurable for each data value in the settings, where you can also select which notifications you want to receive. Notifications can be enabled for Rain start, lightning, and system status changes (such as battery warnings and offline alerts). The app does a good job of limiting repeat notifications to avoid spamming you, so I’ve found it fine to leave them all on.

Along with these key settings are a number of other optional controls. These include:

  • Toggle the forecast view

  • Toggle the battery panes

  • Set Height above ground

  • Toggle Lightning sensor (Air)

  • Toggle power save mode (Sky)

Finally, you can access the raw data values for a number of API variables, such as Station ID, Uptime, Firmware Revision, Last State Change, and many others.

Main App Screen

Main App Screen

Settings Page

Settings Page

Integrations

WeatherFlow has committed to provide any and all platform integrations that make sense. Presently they have Alex and Google Assistant for voice queries, Smart Things and Nest for device integrations, and IFTTT for general automation. HomeKit was intended for release but fell afoul of Apple’s change to their certification requirements for iOS11. WeatherFlow support informs me that they thought a new Hub variant would be required to comply with the security authentication requirements, but they are now looking at leveraging Apple’s software authentication on the existing hub via a firmware update.

I’ve had a minor issue with Alexa, as the WeatherFlow skill is a general skill rather than a smart home one. Every time I ask Alexa for a weather value from WeatherFlow she asks if I’d like to try another weather skill as well, since she only sees it as a generic weather service.

The IFTTT support is particularly interesting, as it allows a vast array of automation options given the wealth of triggers that have been included in the WeatherFlow Service. Many of the data triggers include a ‘rises above’ and ‘falls below’ variant, which is much more helpful than the typical ‘if value equals’ triggers. These options allow for smarter triggering of actions based on what is happening. For example, I have use the temperature rises and falls triggers in conjunction with an air conditioner controller to determine when it should be turned on and off.

By knowing whether it’s getting hotter or cooler I can reliably determine the correct action where a simple value would be ambiguous. Knowing when to turn off the AC is also something that can only be done with external weather data, as that provides the necessary environmental insight to determine if the AC is actually helping, or if it’s just running for no benefit.

The rise/fall options cover temperature, pressure, humidity, light intensity, UV, solar radiation, wind speed (average or gust). Additionally, there are triggers for rain start, lightning strike, and when a new observation is logged.

Security

While weather data is not typically considered sensitive, the security risks around connected devices remain the same; use of the device to gain access to the home network and other devices in the home. WeatherFlow makes the usual claims that they take security seriously, but security is hard, and it’s impossible to be assured of that without seeing the internals of the software. The devices run a ‘purpose-built OS’ which is supposed to mitigate the common exploits of a more general purpose option. This may be true, but it also means no one else has been able to vet the code, so it can go either way.

They seem to have no open ports or protocols, and no remote login facility on the devices. They also encrypt firmware updates with a per-device key to prevent fraudulent injection of malware. This would be dependent on their source server being secure, but it’s certainly another barrier and a good move.

Costs

WeatherFlow offers their back end service free to customers of the device, so the only cost is the upfront purchase and the ongoing battery replacements. A solar option for the Sky would be a really nice upgrade, but Weatherflow is still testing design options at this time. The WeatherFlow Smart Weather Station is currently only available directly through WeatherFlow’s web store. They’ve been sold out, but at the time of writing limited supply had resumed in the North America region. You can take a look at availability on the store page.

Update: 8 May 2019 - Weatherflow has now released a solar panel upgrade module for the Sky sensor which replaces the existing battery solution. The solar panel attaches to the bottom of the Sky between the sensor and the pole mount, and contains an integral 1000mAh battery pack which will run the unit for 30 days without sun. Weatherflow claim that even on cloudy days, there will be sufficient charge to keep the battery pack going. You can pick up the solar upgrade from the Weatherflow store.

Conclusion

Having a wealth of high quality environmental data is a boon to smart home user who want to create more intelligent automation actions. The WeatherFlow Smart Weather Station offers a very cost effective, low maintenance solution using high quality sensors and a wealth of integration options that should meet the needs of many smart home enthusiasts and home weather buffs alike.