Analysis | We mapped weather forecast accuracy across the U.S. Look up your city. (2024)

Everyone complains about the weather forecast, but some people have more cause to grumble than others. In Miami, the temperature forecast is usually accurate a week into the future. But in Paonia, Colo., even the one-day temperature forecast is wrong by almost 6 degrees Fahrenheit on average.

That’s according to our analysis of government data shared publicly for the first time with The Washington Post. The data reveals the broad patterns and the fine contours of the accuracy of the National Weather Service’s official forecast, which triggers the country’s emergency alert systems and powers countless commercial weather products.

To make sense of the data, we made a map of the contiguous United States showing how many days into the future the Weather Service’s forecast of the daily high temperature is accurate within 3 degrees Fahrenheit.

map of weather forecast reliability

Analysis | We mapped weather forecast accuracy across the U.S. Look up your city. (1)

How many days out is the

temperature forecast accurate?

No more than

2 days out

3 to 4

days out

5 to 6 days out

At least

7 days out

In the south of Florida, the forecast is spot-on even a week out

No more than

2 days out

The Great Plains has some of the most unpredictable weather in the U.S.

5 to 6 days out

At least

7 days out

3 to 4

days out

Analysis | We mapped weather forecast accuracy across the U.S. Look up your city. (2)

How many days out is the temperature forecast accurate?

No more than

2 days out

5 to 6 days out

At least

7 days out

In the south of Florida, the forecast is spot-on even a week out

No more than

2 days out

The Great Plains has some of the most unpredictable weather in the U.S.

5 to 6 days out

At least

7 days out

3 to 4

days out

Analysis | We mapped weather forecast accuracy across the U.S. Look up your city. (3)

How many days out is the temperature forecast accurate?

No more than

2 days out

3 to 4

days out

The Great Plains has some of the most unpredictable weather in the U.S.

5 to 6 days out

At least

7 days out

In the south of Florida, the forecast is spot-on even a week out

Analysis | We mapped weather forecast accuracy across the U.S. Look up your city. (4)

How many days out is the temperature forecast accurate?

No more than

2 days out

3 to 4

days out

The Great Plains has some of the most unpredictable weather in the U.S.

5 to 6 days out

The southwest has accurate forecasts 5 to 6 days out

At least

7 days out

In the south of Florida, the forecast is spot-on even a week out

Source: National Digital Forecast Database. The analysis includes forecasts from April 2023 to March 2024.

What’s at stake

The government’s forecast is everywhere.

Both AccuWeather and the Weather Company, the country’s biggest commercial forecasting companies, use the National Weather Service’s forecast, among other data sources. So do farmers and power companies, air traffic controllers and sea captains, smart-sprinkler designers and HVAC manufacturers — and they can all use the data free.

Accurate forecasts save lives.

The National Weather Service’s official forecast powers the emergency alerts that the government distributes to cellphones and TV stations. A recent study found that doubling the forecast’s accuracy would save 2,200 lives every year.

Our map shows the accuracy of the forecast, not the skill of particular forecasters. Some places are just less predictable than others.

Coastal regions can be easier to forecast because the ocean acts like a giant thermal regulator, absorbing the sun’s warmth during the day and gradually releasing it over time. Similarly, the southwest desert is relatively predictable because its arid conditions discourage the formation of disruptive weather systems.

The vast middle of the country lacks these moderating factors. Instead, air masses frequently converge with one another: A warm, moist air mass from the Gulf of Mexico, for example, might surge northward and meet a cold, dry mass sweeping down from Canada. Such interactions can cause rapid, unpredictable temperature swings that throw off the forecast’s accuracy.

The Weather Service has for years measured the accuracy of its official forecast in larger geographic regions, but in November 2022 the organization began testing its accuracy at a much more granular scale. The Weather Service had not shared the more granular data with the public until we asked about it.

With the new dataset, we were able to calculate forecast accuracy in thousands of towns and cities, which you can search below. Because accuracy often varies depending on the time of year, we are also showing the accuracy during the warmer months (April through September) and the cooler months (October through March).

See how accurate the temperature forecast is where you live

Enter a city

Loading data...

Analysis | We mapped weather forecast accuracy across the U.S. Look up your city. (5)Analysis | We mapped weather forecast accuracy across the U.S. Look up your city. (6)

In Washington, D.C., the forecast is accurate4 days out.

Warm months are easier to predict than cool months.

Average forecast error for Washington, D.C.

In predictable places such as Phoenix and Miami, you can choose any date at random — Jan. 20 or June 14 or wherever your dart lands on a year-long wall calendar — and the temperature will be about the same every year. But in a place like Missoula, Mont., next year’s Jan. 20 might be nothing like this year’s.

Winter in Missoula is extra hard to predict because the city sits at the convergence of five valleys, said Lewis Dortch, a meteorologist at the CBS affiliate in western Montana. During winter, cold air sinks down into the city but is too heavy to escape over the surrounding mountains. Instead, the cold gets trapped — sometimes for a day, sometimes for weeks.

During these “inversions,” computer forecasts can be several degrees warmer than the observed temperature, Dortch said. The computer thinks the frigid air has escaped the city, when in reality it’s stuck sloshing around. Then, as suddenly as it formed, the inversion will lift, and the temperature will soar up into the 40s with little warning.

“It’s just one of those things we deal with out here,” Dortch said. “The topography really makes forecasting those temperatures difficult.”

But the prize for the country’s least accurate temperature forecast goes to Paonia, a town of some 1,500 people nestled in the North Fork Valley in the western Rocky Mountains. Like Missoula, Paonia is vulnerable to inversions. On average, Paonia’s 24-hour forecast is off by 5.9 degrees.

“That’s amazing and not surprising,” said Hannah Stevens, executive director of the Western Slope Conservation Center, when told that her hometown has the least accurate one-day weather forecast in the country. “We all look at two to three different weather apps to get some idea of what might be coming. None of them are ever right.”

The Weather Service provided just one year of data, so Paonia may not have the worst forecast every year. Recall, too, that we considered the accuracy of the forecast for only daily high temperature. The Weather Service also assesses its precipitation forecast, but the patterns are a little harder to unpack — especially with just one year’s worth of data — so we stuck with temperature.

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To produce its official forecast, the National Weather Service blends data from 44 computer models — produced by the U.S. government and meteorological services in Australia, Europe and Canada — using a recipe that favors the models with more accurate track records.

To process the data, the Weather Service uses “Dogwood,” a Hewlett Packard Enterprise supercomputer in Manassas, Va., that ranked as the world’s 49th-fastest computer when it was inaugurated in 2022. Its backup, “Cactus,” is located in Phoenix.

Dogwood and Cactus are just the latest weapons in the computational arsenal that has steadily improved the government’s forecasts over time. The National Weather Service does not have long-term accuracy data for its official digital forecast, which it began producing in 2002. But a unit of the Weather Service called the Weather Prediction Center has been producing temperature forecasts since the 1970s.

That data shows steady improvement over the past five decades. “When you were a kid, do you remember the forecast being as good as it is today?” said David Novak, director of the Weather Prediction Center. “It’s one of those quiet revolutions.”

Average error for daily high temperature forecast

Source: NWS Weather Prediction Center. Forecasts are for the contiguous United States.

Even as computer-generated forecasts have improved, the Weather Service still makes room for human expertise. At 122 offices around the country, human forecasters use computer software to edit the official forecast based on their knowledge and experience of local conditions. Those edits tend to be minor, however, and their role has diminished as the computer forecast has improved.

“There’s people considering, what should the future role of the forecaster be?” said David Ruth, the chief of digital forecast services at the Weather Service’s Meteorological Development Lab. “Is it worth our time and effort to actually try to make changes to the model’s first guess?”

As a new generation of AI-powered weather forecasts emerges, the future of the human forecaster looks increasingly dim. Just as chess grandmasters now struggle to discern the brilliant subtleties of far-stronger computer chess programs, human forecasters may soon be unable to grasp the inner workings of the most accurate computer forecasts.

“That makes some people nervous,” Ruth said. “But if the results are good and the verification statistics are good, then, yeah, why complain? We may no longer have the privilege of being able to understand the answer why.”

Dortch moved to Missoula for the scenery rather than the unpredictable weather. Yet he has come to embrace the region’s meteorological unreliability. It means human forecasters like him can still add some value to the brute power of machines such as Dogwood and Cactus.

“I use models, but you can’t always trust the models on surface value. You have to use expertise and experience,” Dortch said. “I like forecasting here, instead of somewhere you just look at the models and read whatever they say.”

Thanks to Simon Ducroquet for the illustrations and to Ian Livingston for the meteorological guidance.

Check our work

The Meteorological Development Laboratory at the National Weather Service provided gridded data on forecast error for daily maximum temperatures. The data is an assessment of the National Digital Forecast Database and spans April 2023 through March 2024. We defined a forecast as accurate if it was within 3°F of the observed temperature. The “ground truth” dataset used for observed temperature is the Unrestricted Mesoscale Analysis. You can find the data and code to produce a map in this computational notebook.

For the lookup tool, the gridded data was averaged over 31,306 “places” across the contiguous U.S. Places are legally incorporated areas such as towns or cities or statistical equivalents drawn up by the Census Bureau, called census designated places. You can find our places dataset in this computational notebook.

Long-term data on the accuracy of U.S. weather forecasts comes from the Weather Prediction Center, a different branch of the NWS. You can find the code and data to produce a chart in this computational notebook.

Analysis | We mapped weather forecast accuracy across the U.S. Look up your city. (2024)

FAQs

How to analyse forecast accuracy? ›

The mean absolute percentage error (MAPE) measures the average of forecast errors in percentages. It's a helpful accuracy metric to use because many people can understand forecast accuracy in terms of percentages. For example, a MAPE of 3% means there was a 3% difference between the actual and projected data.

How do you analyze weather forecast? ›

This is done by examining a large quantity of observation data including surface observations, satellite imagery, radar data, radiosonde data, upper-air data, wind profilers, aircraft observations, river gauges, and simply looking outside.

How can you determine the accuracy of a weather observation? ›

Analyzing the Data:

Compare your forecasted values for each day with the actual observations to determine how accurate your forecasts were. For each temperature value, determine the difference between the forecasted value and observed value.

How accurate is the weather forecast? ›

-Research has shown that a five-day forecast today is generally as accurate as a 24-hour forecast was in 1980. -We can usually forecast your next-day temperature within about 2 to 3 degrees of accuracy. For example, if your forecast high is 60 today, that means the high will usually land between 57 and 63 degrees.

How do you analyze accuracy? ›

How to measure accuracy and precision
  1. Collect data. Begin by recording all the data you have for the project or experiment. ...
  2. Determine the average value. ...
  3. Find the percent error. ...
  4. Record the absolute deviations. ...
  5. Calculate the average deviation.
Jun 24, 2022

What technique is used to determine forecasting accuracy? ›

Answer and Explanation:

The technique of mean absolute percent error (MAPE) is used to determine the accuracy of forecasts by measuring the mean deviation of the forecasted value to the true value in percentage form.

What is the most accurate way to predict the weather? ›

Polar orbiting satellites provide the information most useful for long-term weather forecasting. These satellites use instruments to measure energy, called radiation, emitted by the Earth and atmosphere. This information is incorporated into weather models, which in turn leads to more accurate weather forecasts.

What is the purpose of the weather analysis? ›

Analyses of weather data

In addition to their vital role in weather forecasting, these analyses support scientific investigations designed to help develop improved weather prediction tools and techniques.

What is the weather data analysis? ›

Weather data analysis allows us to understand patterns, trends, and anomalies in weather conditions over time. We will explore how to analyze weather data using the R Programming Language. We will use a dataset containing various weather parameters such as temperature, humidity, wind speed, and more.

Why is forecast accuracy important? ›

Here are some of the benefits of forecast accuracy: Improved decision-making: Accurate forecasts can help businesses make better decisions about inventory, production, and marketing. For example, if a business knows that demand for its product is going to increase, it can increase its production to meet the demand.

How do you make an accurate forecast? ›

Create Realistic, Accurate Forecasts
  1. Begin With Your Baseline. Accurate forecasting is built on an accurate base. ...
  2. Focus On Key Factors. When forecasting, focus on the most meaningful data.
  3. Build From the Bottom Up. When making forecasts, you could work from the top down or the bottom up. ...
  4. Use Good Tools and Be Thorough.

What are the observations of the weather forecast? ›

Observation methods

Temperature, humidity, precipitation, air pressure, wind speed, and wind direction are key observations of the atmosphere that help forecasters predict the weather. These same factors have been used since the first weather observations were recorded.

What is the most accurate weather forecast in the US? ›

The Weather Company, an IBM Business

The world's most accurate forecaster globally, the company reaches hundreds of enterprise clients and more than 400 million monthly active users via its digital properties from The Weather Channel (weather.com) and Weather Underground (wunderground.com).

What is the most accurate weather forecast? ›

July 29, 2021. IBM and its subsidiary The Weather Company continue to be the overall most accurate weather forecast providers worldwide, according to a new study. The Weather Company includes weather.com and other digital properties of The Weather Channel.

How is weather forecast accuracy calculated? ›

Perhaps the simplest way to assess the accuracy of a deterministic point forecast is to calculate the absolute error. The absolute error is merely the absolute value of the difference between the observed and the forecast value (absolute value just means that we're ignoring the sign of the difference).

What is KPI for forecast accuracy? ›

Forecast Accuracy, or forecasting KPIs: Indicating how close the demand forecasts are to actual demand. Monitoring Signals: Indicating whether the demand forecasts are within an acceptable range of error. Bias: Indicating the tendency of the demand forecasts to be systematically higher or lower than the actual demand.

What is the best chart to show forecast accuracy? ›

The run chart of truth: A very popular way to display the forecast error is to visualize the percentage error in a bar chart (a so-called run chart). This is a great way to very easily spot problem areas and trends.

How do you know which forecasting method is more accurate? ›

The selection of a method depends on many factors—the context of the forecast, the relevance and availability of historical data, the degree of accuracy desirable, the time period to be forecast, the cost/benefit (or value) of the forecast to the company, and the time available for making the analysis.

What are the factors affecting forecast accuracy? ›

Highlighting some significant factors that affect Forecasting Accuracy 🔔 The quality and quantity of data used for forecasting have a substantial impact on accuracy. If the data is incomplete, outdated, or contains errors, it can lead to misleading predictions.

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