Last week Sidney de Santa Maria asked for the difference between astronomical seasons and meteorological seasons.
The astronomical seasons are directly related to the tilt of the Earth’s 23½ degree axis as it makes its 365.25 day journey around the sun.
At this time of year, most people yearn for the winter rains, and this year has certainly passed quickly; we have already passed the fall equinox – the onset of fall – which occurred on September 22. Currently, we are near the beginning of October, which loses an average of over 2 minutes of daylight each day.
On Tuesday, December 21, we enter the first day of winter, with the longest night of the year. During this winter solstice, the central coast will only see 9 hours and 44 minutes of sunshine. During the summer solstice in June, our longest day has about 14 hours and 17 minutes of daylight.
If you travel north in June, the days will get longer and longer until you reach the Arctic Circle, where the midnight sun shines and the days never end. But if you did the same in December, the days would get shorter and shorter until you hit the Arctic, with its perpetual darkness.
Unlike meteorological seasons, which have fixed dates, the dates of each astronomical season change from year to year.
Since the solar year lasts approximately 365.25 days, the equinox and solstice occur earlier each year. To remedy this situation, every four years we add an extra day, February 29, to synchronize with our 366-day Gregorian calendar; this is called a leap year. In most years, the spring / vernal equinox usually occurs on March 20 or 21. Last year in 2020, he performed on March 19, the first time since 1896.
As you may have guessed, weather seasons are broken down into four groups of fixed date months.
Winter begins on December 1 and ends on February 28 or February 29 if it is a leap year. Spring is from March to May and summer includes June, July and August. Fall begins on September 1 and ends at the end of November.
Because these dates are set on a monthly calendar, the length of each season is more consistent: 90 days for fall and winter (non-leap years) and 92 days for spring and summer. Ask any climatologist, meteorologist, or weather observer, it is much easier to calculate seasonal weather statistics, such as high and low temperatures, growing degrees of days, or precipitation (rain or snow).
John Lindsey is the marine meteorologist for Pacific Gas and Electric Co.’s Diablo Canyon Power Plant and a media relations representative. Email him at [email protected] or follow him on Twitter @PGE_John.