Phoenix Weather in September
September begins a steady deline in temperature for Phoenix, Arizona. At the same time, rain and thunderstorms become less common.
This page gives detailed information on the typical September temperature, precipitation, sun, humidity, wind and storms for Phoenix. The weather measurements are averages based on climate data gathered at Phoenix Sky Harbor International Airport, located near the city center.
Temperature
| 100 °F | September average high | 38 °C |
| 78 °F | September average low | 26 °C |
| 18 days | 100 °F max. or more (38 °C) |
| 2 days | 70 °F min. or less (21 °C) |
Nearly every day in September heats up to over 90 degrees Fahrenheit (32 degrees Celsius) in Phoenix. At night, the temperature never dips below 60 °F (16 °C) in September.
Rain
| 0.6 in | total precipitation | 14 mm |
| 3 days | of rain |
Half the time, Phoenix receives 0.1 to 0.7 inches (3 to 19 mm) of rainfall in September. One in four years has drier weather, while another one in four is wetter.
Sun
| 89 % | sunshine |
| 22 days | clear skies |
The sun's rays reach the ground in Phoenix during 89 percent of daylight hours on average in September, for a total of 330 hours in the month. Typically on 22 days this month the sky is mainly clear, with at most 30 percent cloud cover.
Sunlight in September at Phoenix lasts for 12 hours and 21 minutes a day on average. The longest day of the month is the 1st with 12 hours and 51 minutes of daylight. By the end of the month, the days have shortened to 11:51 from sunrise to sunset. These durations can vary by a minute or two from year to year.
Humidity
| 36 % | September average humidity |
The relative humidity in Phoenix during September usually peaks at 50 percent in the morning then drops to 23 percent by late afternoon.
| Local Time | 2 am | 5 am | 8 am | 11 am | 2 pm | 5 pm | 8 pm | 11 pm |
| Humidity % | 45 | 50 | 45 | 31 | 24 | 23 | 30 | 38 |
Wind
| 6.3 mph | September wind speed average | 10.1 kph |
September is an average month in Phoenix for wind speed.
Storms
| 0 days | rainfall of 0.5 inches (13 mm) or more |
| 4 days | with thunderstorms in September |
About once a decade, Phoenix receives an inch (25 mm) or more of rain in one day during September.
Reference
The weather data here are long-term averages provided by the US National Centers for Environmental Information (NCEI). Temperature and precipitation are 1991-2020 normals while humidity and thunderstorms are 1961-1990 normals.