What is the 10 day weather forecast? Let's deal with this and other common durations

10 day weather forecast is the key and therefore most common among the forecasts of different durations. You can also see forecasts for 3, 5, 7 and 14 days, and, of course, for today and tomorrow. But what does these numbers actually mean? Could we trust a forecast for more than two weeks or even a month? In this article, you will learn what the 10 day weather forecast is, why it is considered the main one, and about other forecast durations and their accuracy.

What is the 10 day weather forecast?

Let's start a little from afar. Weather forecast is the prediction of weather conditions that will occur in the future. There are several methods to do this.

The most modern and accurate method to predict the weather is numeric modeling. There are well-known physical laws that together can describe how the air moves and how conditions in every spot change. To collect weather data meteorologists use various instruments but mostly special observation weather stations, which are located all over the world. Then they put this data into supercomputers that use those physical laws to turn past and current weather conditions into the weather forecast.

The problem is that the weather cannot be predicted far into the future. In other words, the forecast has time limits. Hence there is such a thing as the duration of the forecast.

10 day weather forecast is the key and therefore most common among the forecasts of different durations. This time period is long enough to plan outdoor activities even for the next weekend. And it’s the longest forecast to have accuracy. But why exactly 10 days?

From the physical laws that describe the atmosphere dynamics, meteorologists know that the atmosphere “forgets” its current state in 14 days. That means that no matter what’s happening with the weather now, in 14 days the current situation can change in any direction. 14 days are called the “theoretical limit” of weather prediction. We can’t predict the weather correctly for more than 14 days. But our methods of weather prediction are still imperfect, so the real limit is a bit lower and equals approximately 10 days. This is where this number of the days comes from.

How accurate is the forecast for 10 days? It is logical to assume that the longer the forecast period, the less accurate it is. So it is about 70% compared to the 1-day forecast, which is the most accurate. It can be lower for mountain areas. Forecast for 10 days can be used for the understanding of the weather conditions, so it is better to double-check it comparing different sources (weather models).

Going back to outdoors, the 10 day-forecast is equally suitable for any sport or activity. But you shouldn’t rely on it in particular values of temperature, wind speed, etc. at 100%. It can be used for a general understanding of the situation: the temperature is rising, the wind is strengthening, and so on. Check also the latest forecasts for extreme weather, if such a weather is possible in your area.

How accurate are weather forecasts with other durations?

1 day weather forecast

The forecast for 1 day has a success rate of about 96–98%. As you can see, even in this case it is not 100%, because to predict the weather with such a probability using even the most modern and powerful computers is still impossible. But you can trust it even in difficult conditions because most future changes in weather can be noticed at least 1 day before they happen. Remember that heavy rain is the hardest event to predict.

3 day weather forecast

3-day weather forecast is the second key type of forecast depending on duration, which is also very common. Speaking about outdoors, this time period is long enough to plan some activities, but at the same time, it’s short enough to have high forecast accuracy.

Again: why three days? That comes from synoptic meteorology: most cyclones and anticyclones live for about a week. And approximately 3 days is the period one particular cyclone or anticyclone influences one particular spot. The weather conditions can be predicted with the highest accuracy in this case. Of course, these are just mean values, and variability all over the world is very high.

The accuracy of the 3 day weather forecast is about 90%. So it suits very well for any sport you can do on flat terrain like city biking, but also in the lake, sea or ocean: kite- and windsurfing, surfing, SUP...

But in different cases, the accuracy can vary. For example, in mountain areas, it’s much lower than on planes, so in the mountains, it’s useful for general understanding of weather conditions but don’t rely on it entirely. The weather in mountains can change frequently, significantly, and unpredictably. If you do sports in the mountains — hiking, cycling, paragliding, skiing and snowboarding, and others, check the latest forecasts if you do your sport in a place where such events are possible — at least for a day.

You should also remember that severe weather events are predicted much worse than calm weather. Extreme weather events (like thunderstorms and so on) can often be predicted only hours before they happen on any territory.

5 day weather forecast

Weather forecast for 5 days has approximately 80% accuracy. It is similar with 3 days forecast because it has a length less than the mean one of cyclones and anticyclones.

7 day weather forecast

The accuracy of 7 days forecast is 70%. It is similar with 3 days and 5 days forecast because it also has a length less than the mean one of cyclones and anticyclones.

14 day weather forecast

Due to physical reasons, the forecast for 14 days is the theoretical limit to predict the weather. Starting with this time any prediction has equal chances to happen or not to happen. The forecast is random.

21 day weather forecast

The period of such a weather forecast is longer than the theoretical limit of the prediction. So the forecast for such a long time shows the way everything could be but can’t show how everything is going to be. It could only be used to check weather conditions that are possible to happen in the area.

30 day weather forecast

The same goes for the weather forecast for a month.

Weather forecast accuracy. Valerya Milovanova / Windy.app

Where to get the 10 day weather forecast?

In the Windy.app for wind sports and outdoors you can find 10 day weather focast in two ways: on the spot and on the Weather Map. Let's take iOS as an example:

10 day weather forecast for the spot

1. Open any spot in the app and find the wind bar. The colors mean wind speed. Choose the day you want to have the forecast for by moving the bar to the right.

2. Select the ECMWF or GFS global weather model above the bar: they give a 10-day forecast. For other models, it may be less: 7, 5, or 3 days.

3. At the same time choose a weather profile for your favorite sport or outdoor activity to have the preset of additional weather elements. At the end of the list you will also find wind speed / gust colors chart.

4. You can also change the forecast step: 1 hour or 3 hours.

5. Remember the weather history? Move the bar to the left to get weather data for the past 10 days, so you now have the weather picture for almost a month.

At the end of the screen, there is also a very useful Weather Archive feature, which shows you the historical weather data for each day and month for the past 10 years (2012-2021). Use it for weather forecasting for longer periods, then 10 days.

10 day weather forecast for fishing in Helsinki, Finland, in the Windy.app for iOS

10 day weather forecast for the world

1. Go to Weather Map from the Home screen of the app or from the Spot screen.

2. Here you have the 10 day forecast for the world with 1 hour step by the same ECMWF (wind) and GFS (precipitation) models.

3. Move the days and choose the hours at the bottom of the screen to see the forecast for the next few days. The choose between wind and precipitation forecast click on the wind gust icon.