No difference

The "moon brings the wind" folklore

"It blows around the full moon." "Moonlit nights are calm." Maritime and mountain folklore preserves sayings about wind and the moon in both directions. Sailors and fishermen have navigated by moon phases for centuries, and since the tides (which the moon really does drive) and the wind blend into one "mood of the sea," linking the two was a natural step.

But the moon's involvement in tides and in wind is of entirely different magnitudes. Tides are driven directly by lunar gravity; wind is driven by pressure differences — that is, by the sun heating the atmosphere unevenly. This page checks "is it windier on full moon days?" against 80+ years of wind records in three cities.

How this verdict is computed

• Data: daily maximum wind speed (10m above ground) from ERA5 (the European reanalysis dataset, since 1940) for three cities — Tokyo, London, and New York — to check whether the conclusion survives a change of location
• Unlike rainfall, wind speed is not a mostly-zero skewed quantity, so averages can be compared directly rather than via a rainy-day-style rate
• Wind is strongly seasonal (Tokyo's spring gales, London's winter storms), so each day is compared with the average wind speed for the same month
• Days are classified as full moon days (±24h around the instant) or new moon days using the moon age at local noon; each group's mean index is compared with 1.00

See the methodology for the exact criteria.

The moon does pull on the atmosphere — barely

Lunar gravity acts on the atmosphere as well as the oceans, producing a tiny pressure wave known as the atmospheric tide. The lunar component amounts to a few tens of pascals at the surface — far smaller than a single isobar on a weather map (hundreds of pascals), and like the ~1% precipitation modulation discussed on the rain page, at the edge of what long-term statistics can detect at all.

So "the moon touches the atmosphere" is real physics. So far, no difference big enough to matter for setting sail or hanging out the laundry has shown up. Still, the moon really does move the air.

What we can't see yet

This result doesn't mean "the moon has nothing to do with it." Here is what the current method can't see:

• Wind at sea: the folklore comes from the sea, but this data is wind over land in three cities
• Wind at the turn of the tide: what fishermen felt may be the wind at the hours the tide turns. A daily maximum can't show those hours

What we want to check next

• Check coastal and offshore wind data
• Line up hourly wind speed with the times of high and low tide

Perhaps the instincts of people who work the sea hold something we haven't yet turned into numbers. We'd like to find it in the data one day.

Sources

• ERA5 reanalysis — generated using Copernicus Climate Change Service (C3S) information (CC BY 4.0); historical data accessed via Open-Meteo
• Moon phase instants computed in-house from Jean Meeus, "Astronomical Algorithms" (UTC)