On Monday, we turn the page of our calendars to March. When speaking in terms of weather and climate, we also begin a new season! Meteorological Spring starts March 1st.
You may be thinking to yourself, "Wait, doesn't Spring begin at the equinox?" Indeed it does. For millennia, people have been using the astronomical calendar to track all four seasons. The natural rotation of the Earth around the Sun forms the basis for this calendar. Seasons are defined by two solstices and two equinoxes. The tilt of the Earth and the alignment of the Sun over the equator determine the solstices and equinoxes. When using the astronomical seasonal calendar, then, Spring begins on March 20th this year.
The meteorological seasonal calendar, in contrast, is based on the annual temperature cycle. Meteorologists and climatologists break the seasons down into groupings of three months. Statistically speaking, Winter (December, January, February) is the coldest time of year and Summer (June, July, August) is the warmest. Spring and Fall are the transitional seasons in between. Therefore, Meteorological Spring includes the entire months of March, April, and May.
By using complete months and monthly increments, it is much easier to compute seasonal "normals" and averages. This allows the general public to better understand weather and climate trends and helps industries such as commerce, energy, and agriculture plan their year.
There are some interesting trends forecast in the Climate Prediction Center's outlook for Meteorological Spring 2021
. Much of the continental United States---especially the Southwest and southern Plains---may witness warmer than normal temperatures. The Northwest could remain below average in the temperature department.
As for precipitation, the Southwest, Great Plains, and Gulf Coast are forecast to remain drier than normal. Parts of the Pacific Northwest, Great Lakes, and New England may end up wetter than normal during this period.
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For WeatherNation, I'm meteorologist Joe Astolfi.