S
M
T
W
T
F
S
30
87°
65°
31
86°
68°
1
93°
72°
2
91°
74°
3
95°
72°
4
88°
69°
5
82°
61°
6
80°
63°
7
80°
63°
8
79°
62°
9
78°
64°
10
80°
65°
11
81°
64°
12
82°
61°
13
79°
60°
14
80°
61°
15
75°
65°
16
74°
64°
17
73°
60°
18
72°
55°
19
71°
56°
20
71°
59°
21
75°
59°
22
77°
62°
23
79°
63°
24
79°
62°
25
77°
61°
26
76°
60°
27
77°
61°
28
76°
60°
29
77°
59°
30
72°
57°
1
68°
54°
2
69°
58°
3
73°
58°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Gaithersburg
Gaithersburg's September 2026 forecast shows daily high temperatures ranging from 68° to 95°, with overnight lows between 54° and 74°. The average high for September is 78° with an average low of 62°. AccuWeather's monthly forecast extends further ahead than any other source, with day-by-day RealFeel® Temperatures giving a complete picture of how September weather will actually feel in Gaithersburg. See also: October | November | December.
