What to Expect for Weather Changes Across the U.S. in September

September, a month that sees the weather change from summer to fall. This month of transition means that you can expect to see a wide array of conditions, regardless of where you live in the U.S. Read on for a deep dive about what to expect during the ninth month of the year.

Temperatures Trend Downward

The falling temperatures is the most noticeable change in September. The arrival of the cooler and crisp air is a telltale sign that fall is coming. In addition to lower afternoon highs, the overnight lows also begin to plummet and serve as a reminder that winter is next.

Average overnight lows in September hover in the 50s and 60s throughout much of the nation with the northern fringes and top terrains seeing lows that drop into the 40s and 30s. The exception to these averages are in Florida, the Gulf Coast, and the Desert Southwest. All three of these regions typically continue to see lows bottom out in the 70s during September.

You will see the most drastic change in the overnight lows by the end of the month. For instance, while Denver sees an average low of 55 degrees to start the month, the temperatures fall into the mid 40s by the time October rolls around.

Despite the arrival of significantly cooler air, many parts of the country will still remain on the toasty side. Widespread highs in the 80s are the story for the southern tier of the U.S. with the Desert Southwest, Texas, and Florida lingering in the 90s and even in the triple digits for afternoon highs.

Looking at a few individual cities, Atlanta comes in with an average high of 87 degrees on September 1. By September 30, the average high struggles to break the 80-degree mark. Up in Minneapolis, the average highs in the upper 70s early in the month slip into the mid 60s by the time September comes to a close.

Shorter Days

With the fall equinox slated for September 22 this year, you can expect the days to begin to get noticeably shorter as the month progresses. The fall equinox marks the time of the year when the sun is shining directly on the equator, translating to equal amounts of daylight for both the Northern and Southern Hemispheres.

Locations in the U.S. located farther to the north will see a larger reduction in daylight hours than areas to the south. Those in the extreme northern parts of the U.S. will experience a loss of over an hour of daylight when comparing the end of September to the beginning. Although the sun rises later each day, it is the earlier sunset times that signal that fall is here.