WHEN DOES FALL BEGIN? There are actually two answers…Meteorological fall begins today, September 1. Astronomical fall begins September 22.
Meteorologists consider fall to be during the months of September, October, and November. By following the civil calendar and having less variation in season length and season start, it becomes much easier to calculate seasonal statistics from the monthly statistics, both of which are very useful for agriculture, commerce and a variety of other purposes. It simply makes for better record keeping.
In terms of astronomy, fall begins at the time of the equinox, when the sun is directly over the equator, and we have 12 hours of daylight and 12 hours of darkness. Traditionally, astronomical seasons last between 89 and 93 days due to the elliptical shape of the Earth’s orbit around the sun. This variability can make it difficult for us to compare statistics from one year to another. Meanwhile, meteorological seasons are more consistent, with the four seasons being broken into groups of three months.
Another hot day on tap for today (highs 90-94), but Friday through the Labor Day Holiday Weekend will have relatively cooler temperatures. Highs Friday through Monday will be around 83-88. However, the tail end of a weak storm system to our north with clip northern Oregon early on Saturday morning. We could see a few sprinkles Saturday morning and this may prevent highs from reaching much above 80 (Saturday). Otherwise, through around September 10 or 11, it's looking dry with a roller-coaster of temperatures. By September 14, data strongly hints that a more steady temperature pattern will kick in. Still don't see signs of a first fall storm - yet.