What the spring equinox really means
Published 7:00 am Tuesday, March 20, 2018
By Skip Rigney
Today is the spring equinox. More precisely, the spring equinox occurs today at 11:15 a.m. That’s the precise moment when the sun will be directly overhead at the equator and the Earth’s axis will have zero tilt, neither toward nor away from the sun. From now until the summer solstice on June 21st, the Northern Hemisphere will gradually be tilted closer to the sun, and there will be more hours of daylight than dark. In the Southern Hemisphere the opposite will be true, as today is their autumn equinox.
You may see today marked on your calendar as “the first day of spring.” But, obviously the spring equinox is not the same as the first day of spring weather.
The changing tilt of one-half of the Earth toward or away from the sun is certainly responsible for the changing of the seasons. However, the advent of the mild temperatures that we think of as being associated with spring doesn’t suddenly happen on March 20th. The change in tilt happens gradually and continuously.
The arrival of spring-like weather depends on one’s distance from the equator and elevation above sea level. Also, global weather patterns, which vary from year to year, affect when spring weather makes its first appearance, and how long it hangs around.
This year the presence of an unusually warm air mass over the eastern U.S. meant that many of our February days felt spring-like. On twenty-one days in February, our high temperatures were warmer than 70 degrees.
However, in March three cold air masses slipped southward from Canada, resulting in several frosty March mornings.
No frost is expected in South Mississippi this week, but the next several nights and mornings will be chilly with low temperatures forecast to be in the 40s. The next several days should be beautiful with sunny skies. Temperatures are forecast to climb into the 60s today and Wednesday, and further warm into the 70s on Thursday and Friday afternoons.
Similar to last workweek, a high pressure system stretching from Canada southward all the way into the Gulf will keep our skies fair. And, similar to this past Saturday and Sunday, the upcoming weekend will find us on the western edge of the ridge of high pressure, which means a weekend return of southerly winds with warmer, more humid air. High temperatures this weekend will be near 80. However, unlike last weekend when a couple of strong low pressure systems over the central Great Plains produced enough instability over our area to generate rain and strong thunderstorms, this weekend looks more tranquil. A slight chance of showers could return by Sunday, but there is a better chance that it will stay dry. And, there is no sign of a repeat of the type of heavy downpours that dumped one to two inches of rain on the southern one-third of Pearl River County this past Sunday. Take the time to enjoy and be thankful for the pleasures of spring this week.
We probably still have many more days of spring weather. But, the blooms on the azaleas are almost gone, the sun is higher in the sky, and April arrives soon.
It won’t be long until we get the first hints of our next, and longest, season.