We British are known for being preoccupied with the weather but, in our defence, we have rather a lot of it. We don’t have a hot season, a rainy season or a snowy season as such, rather there’s a lot of intermingling of seasonal weather.
This summer (2018) was pretty good for a while. We had reliable 23C+ temperature and sunny days from about mid-June until the end of July, but that’s unusual. It has now (late-August) returned to more typical British summer weather: some warm days, some rainy days and some days when it’s even outright chilly, all interspersed in a random fashion.
Such weather makes it tricky to plan anything — like a barbecue, for example — because it could just as easily be a cold day of constant rain as a day hot enough to need sunscreen.
I am led to believe that weather prediction is horrendously difficult and that a butterfly flapping its wings in Hong Kong could spark a tornado in Wigan. As far as I’m aware they can make fairly safe predictions for the next 24 hours and make a reasonable fist of predicting the next three days, but after that it all gets a little fuzzy and they become reliant on long-term probabilities, historical cues and crystal balls.
All this means I have to be reasonable in any assessment I make of a weather app.
The app in question is Dark Sky Weather, which I chose because it is purportedly one of the more accurate weather apps. I’ve read it’s particularly accurate for American weather but I thought I’d see how it fares with the swirling mess that is British weather.
What I did is I used it for a week and each morning at 8AM I looked at the weather it predicted for six hours ahead, 24 hours ahead, three days ahead and seven days ahead. I noted down what the app said about temperature, cloud cover and the percentage chance of rain and then compared that with what the weather actually did.
You can see the data and results I recorded at the end of this post where I’ll talk about accuracy a bit more.
The app itself consists of two main displays: a forecast, which gives you predictions for today and the next seven days, and a weather map, which shows temperature and precipitation in the form of a globe centred on your location. This map can be ‘played’ and it’ll show you how things are likely to develop over the next few days.
You can also set up notifications to remind you take an umbrella or plaster yourself in suncream, depending on what the weather’s going to do on a particular day.
Disappointingly, I had some interface problems on my 2016 iPhone 6 and my 2018 iPad Pro. The weather map struggled to display the temperature overlay from time-to-time and occasionally the forecast for a given day would be blank, only clearing itself by shutting down and restarting the app.
Sometimes, going into the app it wouldn’t give me the forecast screen. I had to switch to map and then back to forecast to make it refresh and present some data.
So there are some glitches and Dark Sky need to polish the app a bit more.
To be honest, the forecast screen was all I was really interested in and this attempts to display all you need to know for the next seven days on one page. It works fairly well and I’d rather tab the various displays on one screen, as Dark Sky does, than page off to another screen.
The forecast screen shows predictions for temperature, feels-like temperature, precipitation, wind, wind gust, humidity, dew point, UV index and cloud cover. The daily views for the next seven days provide an at-a-glance symbol to indicate the weather and minimum and maximum temperatures expected.
As you’ll see from the data table below, Dark Sky made a fairly good go of predicting the weather over seven days. One has to be reasonable when it comes to weather predictions and there are always going to be inaccuracies, particularly with the variable UK weather.
As we’d expect, the longer-term predictions (3 days+) are the ones that suffer the most but the predictions for the next 24 hours are pretty good. I’d suggest Dark Sky predicts the weather as well as any other weather app and better than most of them.
I compared this alongside the BBC’s weather predictions and Dark Sky is certainly the more accurate of the two.
In the table below, I've record what Dark Sky has predicted for temperature, cloud cover and the chance of rain for various time periods. Then, over the course of the week, I've gone back and filled in the results (last column). I've used my own subjective opinion on whether I thought the prediction was "correct" (green), "partly correct" (orange) or "wrong" (red). I've allowed leeway for a few degrees difference in temperature and a few percentage points difference in the chance of rain.
|Saturday 25 August|
|+24H||13C||Mostly Cloudy||31%||Correct, it rained|
|+3D||8C||Partly Cloudy||0%||Mostly correct, although it was warmer than predicted|
|+7D||16C||Mostly Cloudy||8%||Good long-term prediction as it happens|
|Sunday 26 August|
|Now||13C||Rain and Breezy||56%||Correct, it's raining|
|+6H||19C||Rain||83%||Correct, it was pissing down|
|+3D||11C||Partly Cloudy||0%||It was actually spitting with rain and a bit warmer than 11C|
|Monday 27 August|
|Now||15C||Mostly Cloudy||8%||Correct, it's cloudy but not raining|
|+3D||9C||Clear||0%||Not clear and a bit warmer than predicted|
|Tuesday 28 August|
|+24H||15C||Mostly Cloudy||3%||Partly correct, but raining - chance of rain underestimated|
|+3D||12C||Clear||6%||Correct, although chance of rain overestimated|
|Wednesday 29 August|
|Now||14C||Mostly Cloudy||11%||Spitting rain|
|+3D||13C||Partly Cloudy||4%||More or less|
|Thursday 30 August|
|Friday 31 August|
|Now||10C||Partly Cloudy||0%||Nearly. It was actually clear, not a cloud in the sky|
|Saturday 1 September|
I like this app and I’m sure Dark Sky will fix the interface problems I encountered. I’ll be making regular use of this app, anyway, and it will be interesting to see how it copes with the UK winter.