Which Weather API Is Most Accurate?
I build Weather Extension, which lets you choose your weather source. I wanted to know how those sources actually compare, so I spent October saving forecasts and checking them against weather recorded at 15 airports.
Pirate Weather came out ahead for temperature about a day in advance. Visual Crossing led the U.S. comparison and had the lowest wind error.
How Close Were the Forecasts?
For forecasts about 24 hours ahead, Pirate Weather was off by 1.85°F on average. Apple Weather and Visual Crossing followed at just over 2°F.
These five sources were compared on the same forecast hours across all 15 airports. Smaller numbers mean the forecast was closer to what happened.
| Weather source | Average temperature error | Average wind error |
|---|---|---|
| Pirate Weather | 1.85°F | 2.79 mph |
| Apple Weather | 2.06°F | 3.18 mph |
| Visual Crossing | 2.08°F | 2.69 mph |
| MET Norway | 2.41°F | 3.12 mph |
| Open-Meteo | 2.75°F | 3.53 mph |
Pirate Weather also had the lowest temperature error around 6 and 12 hours ahead. By 48 hours, Pirate Weather, Apple Weather and Visual Crossing were almost tied. I wouldn’t choose between them based on that tiny gap.
Visual Crossing’s wind forecasts were closest in all four ranges, though its lead over Pirate Weather was small enough that I wouldn’t call it a clear winner for wind.
What About the National Weather Service?
I compared all six sources at five U.S. airports: JFK, LAX, Miami, Seattle and Chicago.
Visual Crossing had the lowest temperature error at 1.93°F, followed by NWS at 2.09°F, for forecasts about a day ahead.
Which One Would I Use?
I’d start with Pirate Weather for temperature, and give Visual Crossing a look for U.S. forecasts. Then I’d compare them for the places I check most often. The source that wins across several airports won’t necessarily be the closest for your city.
A few tenths of a degree wouldn’t decide it for me. I’d also look at the forecasts I actually use: the next few hours, tomorrow morning, or the weekend. The order can change depending on how far ahead you’re looking.
That’s why I like having a choice of sources in Weather Extension. Try a couple for your area and see which you prefer.
A Note on the Results
These are preliminary October temperature and wind results, updated November 2. They cover this month at these airports, rather than every season or neighborhood. The October rain comparison will follow separately.
You can see the charts, airport scores and detailed comparison or download the October results.