Oh boy, it's downhill from here!
We're sliding into the colder seasons in North America. Here in the North Country, we'll have 12 hours of daylight and 12 hours of night Tuesday, September 25. At least, that is according to select sunrise and sunset calendars for the Burlington area.
Well roughly. That web site shows Burlington having 12 hrs and 2 mins of daylight Tuesday, while the National Weather Service's Daily Climate Report shows an even 12 hour day.
Nonetheless, you may be wondering why this didn't happen during the weekend, when we had our Autumnal Equinox!
So let me enlighten you....get it? On Saturday we had roughly 12 hours and 08 minutes of daylight. However it was the Autumnal Equinox! Well the thing is the Fall season starts when the sun is directly over the Equator. Thus on Saturday, at 10:49 a.m. on the east coast, the sun was at a perfect 90°-angle to the Equator. Generally it generates roughly 12 hours of day and night for both the southern and northern hemispheres.
However it takes a while for the sun to rise, and to set. The atmosphere bends light, as rays enter the particles that compose our sky. So when you see the sun rising above the horizon, the beam is being bent down toward Earth. If you take the 'bend time' off the sunrise and sunset, then you get much closer to that 12 hour split between day and night.
I must give credit to the Fairbanks Museum & Planetarium in Saint Johnsbury, Vermont. Mark Breen's Eye On The Night Sky on VPR discussed this late last week prior to the equinox. The web site is very useful for what is happening with regards to the day and night sky. You can find that info here.
-Meteorologist Steve Glazier