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- On March 1 starts the meteorological spring.
- It’s different from the vernal equinox, which takes place on March 20.
- Weather seasons are based on temperatures, not strictly on the position of the sun.
Meteorological spring arrives on Monday and while you might be itching for the warmer weather, you might be wondering why this happens weeks before the spring equinox.
After a record cold spell and repeated flurries of snow in February, spring couldn’t come soon enough for those affected by crippling power and water outages in Texas and neighboring states.
It turns out that spring is already here, at least according to meteorologists.
The onset of spring that you’ve probably heard of before is known as the vernal equinox.
This is the time when the sun’s most direct rays shine on the equator. In 2021, the spring equinox will take place on Saturday, March 20 at 5:37 a.m. EDT. If you get up early on a weekend morning, you can observe it this year.
Its counterpart in the fall, the fall equinox, as well as the summer and winter solstices, all occur in late September, June, and December, respectively, due to the tilt of the axis of the Earth when it revolves around the sun.
This angle of the sun changing throughout the year is the reason why we have so-called astronomical seasons.
(AFTER: March Temperature Outlook)
The orientation of the Earth in relation to the sun at the spring equinox, summer solstice, fall equinox, and winter solstice of the northern hemisphere.
(NOAA / NWS)
Why do meteorologists deviate from these seemingly concrete definitions?
It all has to do with temperatures.
When you examine the daily high and low average temperatures throughout the year, you will quickly notice a trend.
The three coldest months of the year in the northern hemisphere are generally from the beginning of December to the end of February, while the three hottest months are generally from the beginning of June to the end of August.
These pretty, clean three-month-old buckets are called meteorological winter and summer, respectively.
And those clean three-month temperature buckets don’t line up as well with the astronomical seasons, such as late December through late March.
An example of a generic trace of the average daily high (red) and low (blue) temperatures of the year. The three coldest months of the year are called meteorological winter. The three hottest months are the meteorological summer. The transition between these two elements is spring and fall weather.
(NOAA / NWS)
In fact, Alaska-based climatologist Brian Brettschneider has calculated that the meteorological winter from December 1 to February 28 is better adaptation to the coldest time of the year in most of the United States and Canada.
In one analysis of dozens of American citiesBrettschneider found that only Honolulu, Hawaii, experienced its coldest 90-day period until March.
For those who live in the northern United States, this makes sense.
It seems a bit silly when we say “winter is here” a few days before Christmas, when many parts of the north have already experienced at least one heavy snowfall or cold snap.
Meteorological spring – from March 1 to May 31 – is the transition between the three coldest months and the three hottest months of the year.
Another advantage of weather seasons is the ease of calculating seasonal statistics, since each weather season begins on the first of the month.
A walk of daylight and rising temperatures
Most of the United States will enjoy a full hour of daylight in the evening when daylight saving time arrives on March 14.
Even if there was no daylight saving time, most parts of the northern United States would gain an additional 30 to 45 minutes of evening sun by the end of March. Southern communities would generally only accept 15 to 30 minutes of additional daylight during the month, if our clocks did not jump forward.
Sunset times on March 1 (before daylight saving time) and March 31 (after daylight saving time) in 2021 for various U.S. cities.
(Data: NOAA; Table: Infogram)
While March has a well-deserved stormy reputation, including winter storms in the western and northern United States, with the sun gradually shining higher in the sky, average high temperatures typically rise by around 10 degrees. in the Midwest, Northeast and Plains at the end of the month.
(AFTER: When to expect the 70s and 80s of spring where you live)
Daily high average temperatures on March 1 and March 31 in several US cities. The biggest temperature change during the month occurs in the northern United States, particularly in the plains and the Midwest.
(Data: NOAA; Table: Infogram)
The Weather Company’s primary journalistic mission is to report on the latest weather news, the environment and the importance of science in our lives. This story does not necessarily represent the position of our parent company, IBM.
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