Annual
The Cascade Mountains are the cause of the stark contrast between Eastern and Western Oregon. They form a "rain shadow", effectively shielding the interior parts of the state from precipitation.
Avg. Rainfall
in Inches
< 10
10 - 20
20 - 30
30 - 40
40 - 60
60 - 80
80 - 100
100 - 140
> 140
January
Avg. Rainfall
in Inches
< 1
1 - 2
2 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
> 30
February
Avg. Rainfall
in Inches
< 1
1 - 2
2 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
> 30
March
Avg. Rainfall
in Inches
< 1
1 - 2
2 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
> 30
April
Avg. Rainfall
in Inches
< 1
1 - 2
2 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
> 30
May
Avg. Rainfall
in Inches
< 1
1 - 2
2 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
> 30
June
Avg. Rainfall
in Inches
< 1
1 - 2
2 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
> 30
July
Avg. Rainfall
in Inches
< 1
1 - 2
2 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
> 30
August
Avg. Rainfall
in Inches
< 1
1 - 2
2 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
> 30
September
Avg. Rainfall
in Inches
< 1
1 - 2
2 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
> 30
October
Avg. Rainfall
in Inches
< 1
1 - 2
2 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
> 30
November
Avg. Rainfall
in Inches
< 1
1 - 2
2 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
> 30
December
Avg. Rainfall
in Inches
< 1
1 - 2
2 - 5
5 - 10
10 - 15
15 - 20
20 - 25
25 - 30
> 30
