Meteorological vs Astronomical: When does the season start?

TULSA, Okla. —

September 1st marks the beginning of Meteorological Fall, but Astronomical Fall doesn’t start until September 22nd. What’s the difference and why does it matter?

Meteorological Seasons:

Meteorologists and Climatologists look at the seasons in chunks of 3 months. The months are separated by temperature trends. Winter beings the three months with the coldest average temperatures. Summer featuring the warmest average temperatures. Separating the seasons by month make tracking seasonal statistics and trends much easier.

Spring: March, April, May

Summer: June, July, August

Fall: September, October, November

Winter: December, January, February

Astronomical Seasons:

Astronomical seasons are determined by Earth’s rotation around the sun and alignment of the sun’s rays over the equator. More specifically, the season start dates are marked by an equinox or a solstice. This is a method that has been used for thousands of years. With this method, the start of the seasons can vary by a day or two making weather record keeping a bit more difficult.

Spring: Starts March 20

Vernal Equinox - Day of equal sunshine to the northern and southern hemispheres.

Summer: Starts June 21

Summer Solstice - The sun is at its highest point in the sky for the northern hemisphere. This is the transition to less daylight for the northern hemiphere.

Fall: Starts September 22

Autumnal Equinox - Day of equal sunshine to the northern and southern hemispheres.

Winter: Starts December 21

Winter Solstice - The sun is at it’s lowest point in the sky for the northern hemisphere. This is the transition to more daylight for the northern hemiphere.



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