I pulled "current" weather from wttr.in and the official airport report (METAR) for the same 10 airports in the same minute, then compared them field by field. The obvious conclusion is "wttr.in is wrong." That conclusion is mostly an artifact of the comparison, not the source.
What I did
10 airports. wttr.in "current" vs the latest METAR, pulled in the same minute. Compared wind, temperature, relative humidity, cloud cover.
What I found
- Wind: wttr reports km/h, METAR reports knots. Score them raw and 1.852x of every "difference" is invented by the unit alone. Normalize, and 3 of 10 wind pairs flip verdict (KJFK hit to miss; LFPG and RJTT miss to hit).
- Humidity: METAR never reports relative humidity. You derive it from dewpoint, and 1C of rounding moves it about 6 points.
- Cloud: wttr gives a percent, METAR gives octas. Not the same bin.
- Clock: the two readings sit 3 to 69 minutes apart, so some of the gap is just weather moving.
Left over
Real misses do exist (temp +3/+4C at KSFO and YSSY; wind +8 kt at EGCC), but they are the exception, not the headline.
Verdict
Do not score "wttr lies" before unit, derivation, bin, and clock are pinned.
Every headline is downstream of what you held constant. If your numbers have an obvious answer that smells wrong, that is the job I do.
Work with me
Send one dataset and the question you are trying to answer. I send back the confound and a verdict within 24h.
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n=10, one snapshot. The ruler is mine.
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