Welcome to Astronomical Spring 2017!


Welcome to astronomical spring, as of just prior to 6:30 this morning!  Of course, I say "astronomical spring" because in the world of meteorology, we tend to view March, April and May as the spring season, as that tends to be when weather patterns change.  Of course, snow and cold is often still a part of early spring, but in general, weather patterns begin shifting considerably in the month of March, and that's when we see a noticeably uptick in average daily temperatures.

Astronomical seasons work differently, based upon the solstices and equinoxes.  The onset of spring is marked by the Vernal Equinox - referring to equality of day and night...or at least pretty close to it.  Truly, the Vernal Equinox marks the day and time at which the sun crosses the imaginary line directly above the earth's equator, called the "celestial equator," which very nearly reflects equal day and night length, though not quite - for instance, here in New England we've already passed our closest time of equal day and night, with today bringing 12 hours, 9 minutes and 37 seconds of daylight.

So what else is at work here?  It's all about tilt: the earth's axis tilt of just over 23 degrees means at times we in the Northern Hemisphere tilt toward the sun, at times we tilt away, and sometimes...twice a year...we don't tilt toward or away...we just tilt "sideways" - and those two times are equinoxes.  So, today, the Spring Equinox, our earth still tilts at 23.4 degrees, but finds no solar favor north or south.  So, as we in the Northern Hemisphere ring in the start of astronomical spring, the Southern Hemisphere is heralding in autumn, preparing for their tilt away from the sun in the months to come.

What this all means for us in New England is a big change in weather over the next several weeks.  Take Boston as an example for the region:

  • Our daily average high temperature rises from 46° today, to 78° by the last day of the spring season!
  • Our nightly average low temperature rises from 32° today, to 61° by season's end.
  • Normal rainfall for spring in Boston is 11.5" of precipitation.
  • We gain about 3 hours and 7 minutes of light - from 12 hours, 9 minutes and 37 seconds 15 hours, 17 minutes and 1 second by the last day of spring.

In short, the average spring in New England takes us to a whole new weather world than where we've been, and while it will surely come with some ups and downs (like the arctic air en route for later this week), know that we are rounding the bend quickly to the warmer season.

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