Rockville Weather in September
Average highs run from 77°F on September 1 to 67°F on September 30, and lows from 59°F to 49°F. Normal precipitation for the month is 4.48 in over about 9 wet days.
September day by day
The normal high and low for each date, and the record, in °F.
- Normal low
- Normal high
- Record high
- Record low
September at a glance
- Average high
- 73°F
- Average low
- 54°F
- Precipitation
- 4.48 in
- Record high
- 101°FSep 2, 1953
- Record low
- 27°FSep 30, 1951
- Chance of a freeze
- 3%
- Daylight
- 13 h 07 min to 11 h 47 min
- Cloud cover
- 57%
- Humidity
- 73%
- Dew point
- 54°F
- Wind
- 4.0 mph
Every day of the month
A wet day has at least 0.01 inch of precipitation; snow means at least 0.1 inch of snowfall.
| Date | Normal high | Normal low | Record high | Record low | Chance wet | Chance of snow |
|---|---|---|---|---|---|---|
| Sep 1 | 77°F | 59°F | 96°F 1961 | 44°F 1975 | 28% | 0% |
| Sep 2 | 77°F | 58°F | 101°F 1953 | 41°F 2017 | 28% | 0% |
| Sep 3 | 77°F | 58°F | 101°F 1953 | 40°F 1967 | 28% | 0% |
| Sep 4 | 76°F | 58°F | 96°F 1973 | 44°F 1987 | 28% | 0% |
| Sep 5 | 76°F | 58°F | 93°F 1983 | 44°F 1987 | 28% | 0% |
| Sep 6 | 76°F | 57°F | 96°F 1983 | 40°F 1984 | 29% | 0% |
| Sep 7 | 76°F | 57°F | 95°F 2023 | 37°F 1962 | 29% | 0% |
| Sep 8 | 75°F | 57°F | 96°F 2015 | 39°F 1984 | 29% | 0% |
| Sep 9 | 75°F | 57°F | 93°F 2015 | 38°F 1986 | 29% | 0% |
| Sep 10 | 75°F | 56°F | 94°F 1983 | 37°F 1978 | 29% | 0% |
| Sep 11 | 75°F | 56°F | 99°F 1983 | 39°F 1995 | 29% | 0% |
| Sep 12 | 74°F | 56°F | 92°F 1961 | 36°F 1958 | 29% | 0% |
| Sep 13 | 74°F | 55°F | 91°F 1952 | 40°F 1954 | 30% | 0% |
| Sep 14 | 74°F | 55°F | 90°F 2016 | 37°F 1963 | 30% | 0% |
| Sep 15 | 73°F | 55°F | 88°F 1993 | 35°F 1975 | 30% | 0% |
| Sep 16 | 73°F | 54°F | 92°F 1991 | 33°F 1964 | 30% | 0% |
| Sep 17 | 72°F | 54°F | 90°F 1972 | 34°F 1950 | 31% | 0% |
| Sep 18 | 72°F | 53°F | 88°F 1972 | 36°F 1950 | 31% | 0% |
| Sep 19 | 72°F | 53°F | 93°F 1983 | 33°F 1956 | 31% | 0% |
| Sep 20 | 71°F | 53°F | 95°F 1983 | 30°F 1979 | 31% | 0% |
| Sep 21 | 71°F | 52°F | 91°F 1965 | 31°F 1962 | 31% | 0% |
| Sep 22 | 71°F | 52°F | 94°F 1970 | 32°F 1962 | 32% | 0% |
| Sep 23 | 70°F | 52°F | 92°F 1970 | 34°F 1974 | 32% | 0% |
| Sep 24 | 70°F | 51°F | 92°F 2017 | 30°F 1974 | 32% | 0% |
| Sep 25 | 69°F | 51°F | 91°F 2017 | 30°F 1950 | 33% | 0% |
| Sep 26 | 69°F | 50°F | 93°F 2007 | 33°F 1978 | 33% | 0% |
| Sep 27 | 69°F | 50°F | 89°F 2017 | 30°F 1957 | 33% | 0% |
| Sep 28 | 68°F | 49°F | 87°F 2014 | 31°F 1965 | 33% | 0% |
| Sep 29 | 68°F | 49°F | 85°F 2015 | 30°F 1957 | 33% | 0% |
| Sep 30 | 67°F | 49°F | 91°F 1986 | 27°F 1951 | 34% | 0% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (EDT).
- September 1
- sunrise 6:16 AM, sunset 7:23 PM
- September 30
- sunrise 6:46 AM, sunset 6:33 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USC00068138 (Storrs), public domain. Records: NOAA GHCN-Daily, station USW00014740, every year on file, quality-flagged values removed. Cloud, humidity, wind and sunshine: NASA POWER (MERRA-2, CERES and GEWEX SRB), 1991-2020. The data was obtained from the National Aeronautics and Space Administration (NASA) Langley Research Center's Prediction Of Worldwide Energy Resources (POWER) project funded through the NASA Earth Science Division: POWER Daily API v2, accessed 2026-09-24. Sun and moon: computed with the NOAA solar equations and Meeus.