How Does the Moon Affect the Tides and Weather?

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Plus, let's dispel some Moon myths!

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Learn how the Moon affects planet Earth. From tides to weather, there are many ways that our one and only natural satellite works in tandem with our planet. Plus, let’s dispel some myths about powers that our Moon does NOT have!

How the Moon Affects Tides

Ocean Tides

Of course, high tides and low tides are caused by the Moon’s gravitational pull. People have always noticed the Moon’s synchronicity with the timing of the five-foot average rise and fall of the oceans at shorelines around the world.

The Moon’s gravity causes our oceans to bulge out on the side closest to the moon and the side farthest from the moon. These bulges of water are high tides. The low points are where low tides occur.

Tides have a significant effect on the weather, affecting the movement of ocean currents. In turn, this affects the weather through the amount of warming or cooling water moving through a given area.

Ground Surface Tides

The Moon doesn’t only affect ocean tide. The ground itself rises and falls. Earth’s ground tides amount to less than 8 inches (20 centimeters). It’s not perceptible like water which moves around much easier.

The Earth’s crust flexes in the direction of the tidal pull. Satellites which can measure the Earth’s topology confirm that the Moon affects the height of the land and puts stress on tectonic faults. Some scientists hypothesize that these shifts might affect earthquakes and even volcanoes.

The Tidal Fish, Turtles, and Sea Life

Something we don’t often think about is that the Moon not only affects the tides rising and falling, but also many of the animals in the sea have come to rely on the tides and movement of the oceans and lakes. Some species of fish and turtles lay eggs or hatch based on the tides so that their offspring survive. Certainly, lack of fish would affect the entire food chain including humans. On a related note, the Moon phases also trigger reproduction and feeding for many sea creatures who rely on the light of the Moon.

How the Moon Affects Weather

Air Pressure

And in the 1990s, science confirmed the Moon’s ability to generate an atmospheric tide, a gaseous pulse that creates daily changes in air pressure. It also alters circulation patterns such as the subtropical high pressure belts. These may help explain amazing yet subtle links—recognized for the past half-century—between lunar phase and cloudiness, hurricane formation, and precipitation.

So, yes, the Moon definitely influences the weather.

Lunar phase

Want another effect? At the time of full Moon, the temperature of the lower four miles of atmosphere increases by two hundredths of a degree Fahrenheit. That’s not enough to let you leave your jacket home on moonlit nights, but it does provide new theories to explain the link between weather and lunar phase.

Thunderstorm Activity

Other researchers think the statistical increase in thunderstorm activity observed around the full Moon may be caused by our planet’s magnetic tail undergoing moon-induced distortions. Other theorists suggest clouds are “seeded” by the Moon’s modulation of meteor dust. Studies from 2014 and 2016 confirm a one percent rainfall variation caused by the Moon’s phases and position.

Thermal Action

Back in 1995, University of Arizona investigators surmised that the Moon’s action may be primarily thermal, caused by infrared emission from its hot, 230ºF, sun-lit surface, aimed at us like an electric bathroom heater.

The ability of the Moon to reflect sunlight is minimal because the Moon is one of the least shiny objects in the known universe. It reflects just 10% of the sunlight that strikes it, which matches the reflectivity of an asphalt road. In other words, the Moon is no brighter than if its surface were entirely paved like an enormous mall parking lot. That’s why the full Moon is half a million times less bright than the Sun. It appears white only because of its contrast with the even-darker night sky behind it.

How the Moon Affects Climate

Without a Moon, Earth would experience more extreme climate change. Both the Earth and the Moon have gravity and pull at each other. The Moon’s gravity help the spinning top of Earth rotate more smoothly without wobbling more erratically. The Earth would tilt further and cause the poles to be hotter or colder with big differences in temperature. The Moon helps stabilize our climate so it’s less turbulent than other planets.

Myths About the Moon

It’s not a weird idea to think that the Moon causes trouble for us down here on Earth. Some of these age-old myths have been embraced for a long time (and still are):

  • The word “lunatic” comes from the ancient belief that the Moon could cause mental illness!
  • Because the average menstrual cycle length is 29 days and the lunar cycle lasts 29.5 days, there was a belief that lunar phases influenced the menstrual cycle.
  • Many medical professionals in maternity wings will insist that births increase during the full Moon phase. 
  • Others thought crime increased near the full Moon.

However, none of that is true…

  • The full Moon does not foster mental illness; this is confirmed by the utter lack of increased psychiatric hospital admissions during that time.
  • Year-long studies have not shown synchrony of lunar phases with the menstrual cycle. If a woman’s cycle happens to be on that sequence (and some are), it’s a coincidence.
  • While medical professionals often report that strange things happen on a full Moon, there is no significant difference in the frequency of births across the eight stages of the Moon.
  • And a Dade County (FL) study found no link to crime.

How does the Moon affect humans? It affects our sleep! Read more about how the Moon affects on our moods and wellbeing.

Moon and Weather Folklore

The next time that you look up at the Moon, consider this age-old weather folklore from our Almanac archives. Does any of this ring true in your experience? 

    •    In the wane of the Moon, a cloudy morning bodes a fair afternoon.  
    •    If the crescent Moon holds its points upward, able to contain water, it predicts a dry spell.  
    •    If the new Moon stands on its points, expect precipitation to spill out.  
    •    A winter full Moon is a time for long cold snaps.  
    •    A full Moon in April brings frost.  
    •    Sailors agree that the full Moon “eats clouds.”  
    •    Two full Moons in a month increase the chances of flood.  
    •    A pale full Moon indicates rain, while a red one brings wind.  
    •    A Christmas full Moon predicts a poor harvest.  
    •    The days following a new Moon or a full Moon are typically stormy.

Love folklore? See if you recognize any of these weather sayings and discover their meanings.

About The Author

Bob Berman

Bob Berman, astronomer editor for The Old Farmer’s Almanac, covers everything under the Sun (and Moon)! Bob is the world’s most widely read astronomer and has written ten popular books. Read More from Bob Berman

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