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FOR THE
FOREST INDUSTRY
OCTOBER I960
CLIMATOLOGICAL NOTE NUMBER 50
FREQUENCIES OF DAILY EXTREMES IN TEMPERATURE IN THE NORTH
WILLAMETTE AREA (BONNEVILLE, DALLAS, ESTACADA)
Question: "During a given 10-day period in the North Willamette area of Oregon, what is the
likelihood that daily extremes in temperature will be seasonably high or low?"
Table 1:
The values tabulated are based on actual observations of daily maximum tem
perature made at the stations indicated during the years 1949-58, and are pre
sented on the basis of "days in 100 days". The numbers 0, 1, 2, and 3 above
the data columns stand for classes of maximum temperature as follows:
0
maximum temperature below 30 F
1 maximum greater than 29 F, but less than 60 F
2
3
maximum greater than 59 F, but less than 90 F
maximum greater than 89 F
That is, during the first third of January at Bonneville, daily maximum tem
peratures are most likely to be between 29 F and 60 F (class 1), this class
having occurred at the rate of 89 days in 100 days. Seasonably low maximum
temperatures (in this instance, class 0) and seasonably high temperatures
(class 2) have occurred at the rates of 10 and 1 days in 100 days, respectively.
Combining these statements, one sees that during the first third of January at
Bonneville seasonably normal temperatures (class 1) account for 89 per cent
of the days, and of those remaining, 10/11 or 91 per cent, are seasonably low.
Similar combinations of the data may be made for Dallas and Estacada and for
other periods of the year.
Table 2:
This Table presents data on daily minimum temperatures during the same
years in a manner similar to that of Table 1. However, the numbers 0, 1,2,
and 3 in this Table stand for different temperatures than those in Table 1, as
follows:
0
minimum temperature below 0 F
1 minimum greater than -IF, but less than 30 F
2 minimum greater than 29 F, but less than 60 F
3
minimum greater than 59 F
OREGON
•REST
LANDS
RESEARCH
FOREST
RESEARCH
CENTER
CORVALLIS
Table 1. Frequency of Daily Maximum Temperatures in the North Willamette Area,
as Days in 100 Days.
Period
1
0
2
Estacada
Dallas
Bonneville
0
3
2 1
1
1
0
3
3
2
4
96
2
96
7
93
2
96
2
i - 10
10
89
1
2
98
1]1 - 20
15
84
1
2
96
21 i - 31
26
74
7
93
I - 10
12
86
3
94
3
1]I - 20
1
97
3
98
2
21 L - 29
1
99
94
5
86
14
93
7
L - 10
94
6
94
6
95
5
Mar. 1]I - 20
95
5
86
14
87
13
16
Jan.
Feb.
Apr.
May
June
2) I - 31
91
9
79
21
L - 10
67
33
52
48
56
44
1]I - 20
50
50
42
58
46
54
2]l - 30
46
54
40
60
47
52
L - 10
33
67
20
80
26
74
1]I - 20
25
74
I
10
86
17
80
2] t - 31
17
82
1
8
92
4
Sept.
Oct.
Nov.
87
91
9
87
4
91
92
3
6
2
1]I - 20
8
90
2
97
3
6
97
3
92
8
2
1
3
3
13
82
i:I - 20
1
5
16
8
88
12
89
10
93
7
78
22
87
13
89
21I - 31
1
95
4
86
14
93
7
I - 10
1
97
2
86
14
90
10
85
15
92
7
1]I - 20
92
8
81
19
21L - 31
94
6
88
12
81
19
90
10
9
91
8
94
6
10
85
5
87
2
1
91
8
1
95
4
91
2]L - 30
7
92
1
L - 10
25
75
28
72
91
53
47
60
67
33
74
26
76
24
90
6
90
6
93
7
93
7
99
1
100
99
1
98
2
99
1
98
2
11
1]L - 20
36
64
9
21L - 31
67
33
40
L - 10
"87
13
92
3
1]I - 20
5
95
L - 10
1
99
11L - 20
2
2]I - 31
4
96
96
5
2
4
1
1
I - 10
1]L - 20
211 - 30
Dec.
4
I - 10
I - 10
Aug.
2
84
21 I - 30
July
2
2
4
•
.
Table 2.
Frequency of Daily Minimum Temperatures in the North Willamette Area,
as Days in 100 Days.
Dallas
Bonneville
Feb.
Mar.
May
June
July
1
1^
64
35
65
11 - 20
32
68
37
63
32
68
39
60
21 - 31
1
41
58
1
40
59
1 - 10
4
2
1
23
73
28
70
25
75
11 - 20
14
86
«£o
72
16
84
21 - 29
13
87
29
71
20
80
1 - 10
15
85
30
70
27
73
11 - 20
6
94
30
70
13
87
21 - 31
2
98
14
86
7
93
100
11
89
2
98
11 - 20
100
4
96
21 - 30
100
7
93
1 - 10
99
4
96
11 -
1
3
100
1
99
100
100
100
98
21 - 31
100
100
100
1 - 10
94
6
99
1
100
11- 20
96
4
99
1
98
21 - 30
95
5
99
1
100
1 - 10
82
18
98
2
99
1
20
69
31
96
4
99
1
21 - 31
84
16
100
99
1
2
11 -
20
2
2
85
15
99
1
98
20
77
23
99
1
100
21 - 31
84
16
99
1
99
1
99
1
99
1
1
11 -
20
21 - 30
11 - 20
18
97
91
9
100
97
3
100
99
100
82
1 - 10
1
21 - 31
3
100
1
99
99
4
96
3
97
100
5
95
3
97
100
15
85
4
96
11 - 20
8
92
17
83
10
90
21 - 30
8
92
28
72
20
80
87
1 - 10
Dec.
3
36
1 - 10
Nov.
Estacada
0
73
Sept. 11 -
Oct.
2
27
1 - 10
Aug.
1
1 - 10
1 - 10
Apr.
0
1
0
Period
Jan.
3
2
1 - 10
10
90
19
81
13
11 - 20
12
88
20
80
17
83
21 - 31
19
81
33
67
22
78
As with maximum temperatures, one may compute that in the first third of
January at Bonneville, for instance, seasonably normal minimum tempera
tures (in this instance, class 2) account for 73 per cent of the days, while, of
those remaining, 27/27, or 100 per cent, are seasonably low (class 1).
The data: One must keep in mind that observations of temperature summarized in these
Tables were made about five feet above ground in official instrument shelters
of the U.S. Weather Bureau at stations indicated.
Not only will temperatures
vary from place to place at a given time, but also they will be different nearer
the earth's surface or farther from it than in the official shelter.
In short,
tabulated values presented here cannot be considered more than suggestions
of the patterns in time and space of temperatures occurring on a given day.
Even with these various restrictions on interpreting the data, they will give
the reader a rough idea of the levels of extreme temperatures likely at
different times of the year in the North Willamette area of Oregon.
Similar data for Portland and Salem are available in detail as Climatological
Notes 42 and 43 of this series.
In addition, detailed information on dates of
last freeze in the spring and first freeze in the fall at various locations in
Oregon will soon be made available in a publication by the Oregon Agricultural
Experiment Station, Corvallis.
William P. Lowry,
In Charge, Forest Meteorology