September 1 marks the beginning of autumn, or meteorological autumn. Meteorologists use a slightly different schedule for the seasons than the astronomical seasons we learned in school.

Meteorologists are beginning a slow transition into the coldest months of the year. Everyone else who isn’t ready to let go of summer quite yet can enjoy the next few weeks. Astronomical fall officially begins on Sunday, September 22nd, at around 6:44 a.m. MDT.

During the spring and autumn equinoxes, the center of the sun is directly over the equator. This means that day and night are the same length in the northern and southern hemispheres. The days are longer in summer, and the shortest daylight hours are in the winter months.

Okay, so much talk about astronomical and meteorological precipitation. So what’s the difference? Meteorological precipitation occurs on the same dates every year, from September 1st to November 30th. This is done for record-keeping purposes. Astronomical precipitation begins on September 23rd and lasts until December 20th. This is based on the Earth’s position in relation to the Sun and the dates can vary from year to year.

The average high temperature of 66 degrees is a bit misleading. The average high temperature in August is 88 degrees, in September 80 degrees, and in October 65 degrees.

Next fall, temperatures are expected to be above average and rainfall below average.

The current fall forecast for September, October and November calls for below average precipitation (40-50%). The chance of above average temperatures is between 40 and 70%, with the chance increasing as you move closer to the southwestern corner of the state.