S
M
T
W
T
F
S
30
77°
45°
31
85°
46°
1
85°
56°
2
76°
51°
3
71°
46°
4
73°
47°
5
69°
48°
6
65°
47°
7
74°
48°
8
79°
45°
9
83°
44°
10
81°
50°
11
76°
46°
12
76°
50°
13
60°
48°
14
71°
42°
15
68°
49°
16
77°
47°
17
78°
46°
18
82°
47°
19
84°
47°
20
87°
48°
21
86°
48°
22
81°
48°
23
76°
49°
24
78°
52°
25
77°
52°
26
74°
50°
27
76°
52°
28
74°
51°
29
75°
49°
30
74°
50°
1
73°
46°
2
76°
51°
3
70°
46°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
September Weather in Prosser
Prosser's September 2026 forecast shows daily high temperatures ranging from 70° to 87°, with overnight lows between 46° and 52°. The average high for September is 78° with an average low of 49°. 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 Prosser. See also: October | November | December.
