Rockville weather in September: Rockville, Maryland: normal highs, lows, rain and records for September
Rockville in September has a normal high of 78°F and a normal low of 60°F, a daily mean of 69°F, falling from 82°F on the 1st to 72°F by the 30th. Measurable precipitation falls on 10 days in a normal September, 4.01 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 25°C and low of 16°C, 102 mm of precipitation in September.
- NOAA stationRockville (1 mi NE)
- Station IDUSC00187705
- Location39.10°N 77.15°W
- Elevation440 ft (134 m)
- From the center1 miles
- Population68,417
- Jan 42° 27°
- Feb 45° 28°
- Mar 54° 36°
- Apr 66° 46°
- May 74° 55°
- Jun 82° 64°
- Jul 87° 69°
- Aug 85° 67°
- Sep 78° 60°
- Oct 66° 48°
- Nov 56° 38°
- Dec 46° 31°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Rockville in September?
The normal high is 78°F and the normal low 60°F, for a daily mean of 68.7°F. September is 7.2°F cooler than August and 11.7°F warmer than October. September is the 4th warmest month of the year in Rockville and the wettest. Across the month the normal high falls 10°F, from 82°F on September 1 to 72°F on September 30. From one year to the next September's mean temperature typically moves about 2.2°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 67°F and 71°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 31%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 82°F | 65°F | 28% | 18% |
| September 8 | 80°F | 63°F | 29% | 18% |
| September 15 | 78°F | 61°F | 30% | 19% |
| September 22 | 75°F | 58°F | 31% | 19% |
| September 30 | 72°F | 54°F | 30% | 18% |
Every day of September: normal high, low and chance of precipitation (warmest afternoon September 1, coldest night September 30)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| September 1 | 82°F | 65°F | 28% | 18% | 13 h 10 min |
| September 2 | 82°F | 64°F | 28% | 18% | 13 h |
| September 3 | 82°F | 64°F | 28% | 18% | 13 h |
| September 4 | 82°F | 64°F | 29% | 18% | 13 h |
| September 5 | 81°F | 64°F | 29% | 18% | 13 h |
| September 6 | 81°F | 63°F | 29% | 18% | 12 h 50 min |
| September 7 | 81°F | 63°F | 29% | 18% | 12 h 50 min |
| September 8 | 80°F | 63°F | 29% | 18% | 12 h 50 min |
| September 9 | 80°F | 63°F | 29% | 18% | 12 h 50 min |
| September 10 | 80°F | 62°F | 30% | 18% | 12 h 40 min |
| September 11 | 79°F | 62°F | 30% | 19% | 12 h 40 min |
| September 12 | 79°F | 62°F | 30% | 19% | 12 h 40 min |
| September 13 | 79°F | 61°F | 30% | 19% | 12 h 40 min |
| September 14 | 78°F | 61°F | 30% | 19% | 12 h 30 min |
| September 15 | 78°F | 61°F | 30% | 19% | 12 h 30 min |
| September 16 | 78°F | 60°F | 30% | 19% | 12 h 30 min |
| September 17 | 77°F | 60°F | 30% | 19% | 12 h 30 min |
| September 18 | 77°F | 59°F | 31% | 19% | 12 h 20 min |
| September 19 | 76°F | 59°F | 31% | 19% | 12 h 20 min |
| September 20 | 76°F | 59°F | 31% | 19% | 12 h 20 min |
| September 21 | 76°F | 58°F | 31% | 19% | 12 h 20 min |
| September 22 | 75°F | 58°F | 31% | 19% | 12 h 10 min |
| September 23 | 75°F | 57°F | 31% | 19% | 12 h 10 min |
| September 24 | 74°F | 57°F | 31% | 19% | 12 h 10 min |
| September 25 | 74°F | 56°F | 31% | 19% | 12 h 10 min |
| September 26 | 73°F | 56°F | 31% | 18% | 12 h |
| September 27 | 73°F | 56°F | 30% | 18% | 12 h |
| September 28 | 73°F | 55°F | 30% | 18% | 12 h |
| September 29 | 72°F | 55°F | 30% | 18% | 12 h |
| September 30 | 72°F | 54°F | 30% | 18% | 11 h 50 min |
- Normal high
- 78°FSeptember average
- Normal low
- 60°FSeptember average
- Precipitation
- 4.01 inmonth total
- Days with precipitation
- 100.01 inch or more
- Days at 90°F or more
- 1
- Daylight
- 13 h 10 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 24
- Days at 80°F or more
- 12
- Sunshine
- 75%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USC00187705; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Rockville in September?
On a given September day the chance of 0.01 inch or more is 30% on average, highest around September 22 (31%). In all, 4.01 in falls on 10 days of a normal September, 1 of them with an inch or more.
In a normal September in Rockville, 1 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USC00187705.
What are the records for September in Rockville?
The warmest September temperature on this station's record (since 1907) is 99°F, on September 6, 1954; the coldest is 28°F, on September 24, 1974. The wettest September brought 11.37 in (1979).
Source: records: ACIS, station USC00187705. Records and recent months use complete months only.
How does September in Rockville compare across Maryland?
Across the 26 places PlainClimate covers in Maryland, September normal highs run from 72°F in Frostburg to 82°F in Snow Hill; Rockville's is 78°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.