Are you ready for September already? Meteorological summer ends Saturday and we kick off another new season for the Washington area this holiday weekend. September customarily delivers some summery heat for a while, but also mixes some early season chill at times, too.

We project warmer than normal temperatures this September and slightly below normal rainfall. We’re looking for temperatures about two to three degrees above normal and rainfall about 0.25 to 1.0 inches below normal.

September is typically our 4th warmest month of the year (average temperature is 71 degrees) and the wettest month of autumn (average rainfall is 3.72 inches).

The big question is how many more 90-degree days are ahead of us? We have some low to middle 90s coming back into play on Tuesday to Wednesday next week and again potentially two weeks from now. Looking back at all the years to 2010 shows that it is quite common for us to at least a few more 90-degree days in September:

Explaining our outlook

El Niño fades. The warmer than normal ocean water in the central tropical Pacific, indicative of El Niño, has faded and the atmospheric response, which often introduces increased moisture in our region, has waned. This led us to a drier than expected August and it looks like September may follow.

Models. The NOAA CFS model supports this dry idea but we’re not so moisture-starved we need to start worrying about drought.

The model also supports our temperature forecast showing near to slightly above normal temperatures in the eastern U.S:

The precipitation forecast is below:

September’s big wild card for rainfall is Atlantic hurricane season: The season reaches its peak in mid-September and it only takes one storm’s remnants to flip September from a dry month to a wet one.

The incoming Hurricane Dorian is currently expected to remain south and east of the D.C. area. The American model ensemble keeps us in the rain shadow over the next ten days with minimum rainfall forecast: