S
M
T
W
T
F
S
30
75°
46°
31
85°
52°
1
68°
57°
2
64°
55°
3
63°
54°
4
65°
53°
5
73°
53°
6
64°
56°
7
73°
52°
8
82°
51°
9
88°
52°
10
83°
53°
11
72°
47°
12
65°
54°
13
63°
50°
14
71°
53°
15
69°
48°
16
82°
49°
17
87°
51°
18
69°
52°
19
73°
47°
20
78°
47°
21
73°
52°
22
N/A
23
71°
49°
24
71°
46°
25
64°
48°
26
66°
48°
27
73°
43°
28
68°
48°
29
69°
55°
30
70°
51°
1
76°
52°
2
73°
50°
3
75°
52°
Temperature Graph
°F
Avg. Hi
Avg. Lo
Actual Hi
Actual Lo
Forecast Hi
Forecast Lo
*Temporarily Unavailable
September Weather in Lake Oswego
Lake Oswego's September 2026 forecast shows daily high temperatures ranging from 66° to 76°, with overnight lows between 43° and 55°. The average high for September is 71° with an average low of 50°. 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 Lake Oswego. See also: October | November | December.
