S
M
T
W
T
F
S
30
68°
56°
31
79°
53°
1
73°
52°
2
76°
58°
3
70°
53°
4
70°
48°
5
74°
54°
6
76°
48°
7
67°
50°
8
75°
49°
9
78°
55°
10
74°
51°
11
64°
50°
12
71°
47°
13
75°
47°
14
77°
50°
15
74°
49°
16
73°
48°
17
72°
49°
18
73°
50°
19
71°
49°
20
70°
46°
21
67°
50°
22
65°
47°
23
64°
46°
24
66°
50°
25
67°
50°
26
63°
48°
27
63°
45°
28
62°
43°
29
61°
41°
30
61°
42°
1
67°
47°
2
69°
48°
3
69°
48°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Sumas
Sumas's September 2026 forecast shows daily high temperatures ranging from 61° to 78°, with overnight lows between 41° and 55°. The average high for September is 69° with an average low of 48°. 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 Sumas. See also: October | November | December.
