All forecasts are not created equal. (Weather Underground)

We get the question all the time — which app has the most accurate forecast? The truth is, it depends on where you’re located. Some companies do better at forecasting in Chicago than, say, San Francisco. Some methods are going to be better-suited for Midwest winters than Santa Ana winds.

But unless you have the patience to track the accuracy of multiple apps over a few weeks’ time, you’re probably better off trusting an independent forecast “grader,” like ForecastWatch, which has been monitoring accuracy for over a decade.

Every once in a while, ForecastWatch performs a comprehensive study on the biggest weather predictors, such as the Weather Channel, AccuWeather and the National Weather Service, and international companies such as Foreca and MeteoGroup. One of these analyses was published last week, and it included forecast data from 11 forecast providers from 2010 to 2016. In total, over 142 million forecasts were analyzed, according to ForecastWatch’s overview.

When it was all said and done, the world’s most accurate forecasts came from these companies:

1. The Weather Channel (weather.com)

2. MeteoGroup

3. Weather Underground (sister company to the Weather Channel)

4. Foreca

ForecastWatch looked at U.S. and international forecasts:

Forecasts from three regions and three days-out groupings were analyzed. Forecasts were collected from 2010 through June of 2016 for the United States, and from 2013 through June of 2016 for Asia-Pacific and Europe.

The study had a clearly defined and objective bar to meet:

Accuracy was measured as the combination of the percentage of high temperature forecasts within three degrees, the percentage of low temperature forecasts within three degrees, and the percent correct of precipitation forecasts.

It was also exhaustive:

Forecasts from eleven different providers were collected for a total of over 142 million forecasts analyzed.

One of the most important things to consider when you’re ranking a forecast is how many days into the future it’s trying to predict. A Day 7 forecast is less accurate than a forecast for tomorrow.

ForecastWatch broke the results down into three useful periods: 1-3 days, 3-5 days and 6-9 days. These are the accuracy results for U.S. forecasts:


U.S. forecast accuracy from 2010 to June 2016. (ForecastWatch)

As computing power increases, forecast methods are rapidly changing. These results may not be the same in a year, but for now, you know which app to download the next time you’re planning an event — or just wondering whether it’s going to rain tomorrow.