Freeze/Frost Occurrence Data, 1961-90, Montana, USA 1/
 
Station County Temp
Threshold
(Deg. F)
Spring (Date)
Probability Level
Fall (Date)
Probability Level
Freeze Free Period
Probability Level
90 50 10 10 50 90 10 50 90
Belgrade AP Gallatin 36
32
28
May 29
May 09
Apr 24
Jun 20
Jun 03
May 09
Jul 12
Jun 27
May 24
Aug 20
Aug 28
Sep 08
Sep 04
Sep 12
Sep 23
Sep 19
Sep 27
Oct 09
102
133
159
75
101
137
48
69
114
Big Sandy Chouteau 36
32
28
May 21
May 07
Apr 22
Jun 08
May 25
May 09
Jun 26
Jun 12
May 25
Aug 19
Sep 01
Sep 09
Sep 04
Sep 14
Sep 24
Sep 19
Sep 28
Oct 09
113
133
157
87
112
138
61
90
119
Big Timber Sweet
Grass
36
32
28
May 15
May 02
Apr 19
Jun 05
May 18
May 01
Jun 26
Jun 03
May 12
Aug 25
Sep 04
Sep 15
Sep 09
Sep 20
Oct 02
Sep 24
Oct 06
Oct 20
125
149
175
95
124
154
65
99
132
Bigfork 13 S Flathead 36
32
28
May 16
Apr 30
Apr 05
Jun 02
May 16
Apr 24
Jun 19
May 31
May 12
Aug 29
Sep 11
Sep 22
Sep 17
Sep 29
Oct 14
Oct 06
Oct 17
Nov 06
134
159
205
106
136
173
78
113
141
Billings
Water Plant
Yellowstone 36
32
28
May 11
Apr 25
Apr 18
May 26
May 12
Apr 30
Jun 10
May 29
May 12
Sep 01
Sep 06
Sep 18
Sep 14
Sep 23
Oct 04
Sep 28
Oct 10
Oct 21
133
156
178
111
133
157
89
110
135
Bridger Carbon 36
32
28
May 12
Apr 27
Apr 17
Jun 05
May 16
May 02
Jun 28
Jun 04
May 17
Aug 27
Sep 06
Sep 18
Sep 10
Sep 20
Oct 03
Sep 23
Oct 05
Oct 18
125
151
173
97
127
153
68
102
134
Broadus Powder
River
36
32
28
May 10
May 01
Apr 20
May 31
May 19
May 06
Jun 22
Jun 07
May 21
Aug 20
Aug 31
Sep 10
Sep 05
Sep 14
Sep 24
Sep 21
Sep 28
Oct 08
123
140
158
96
117
140
69
94
122
Chester Liberty 36
32
28
May 30
May 17
Apr 29
Jun 23
Jun 06
May 15
Jul 17
Jun 26
Jun 01
Aug 12
Aug 27
Sep 03
Aug 27
Sep 08
Sep 17
Sep 12
Sep 21
Oct 01
92
118
145
64
94
124
37
70
103
Chinook Blaine 36
32
28
May 16
May 03
Apr 18
Jun 02
May 16
May 04
Jun 19
May 29
May 20
Aug 22
Sep 03
Sep 09
Sep 06
Sep 16
Sep 23
Sep 22
Sep 29
Oct 08
116
140
162
96
122
142
77
104
122
Conrad
Airport
Pondera 36
32
28
May 30
May 12
Apr 30
Jun 19
May 27
May 13
July 09
Jun 12
May 25
Aug 17
Aug 28
Sep 07
Sep 02
Sep 14
Sep 23
Sep 19
Sep 30
Oct 09
103
133
151
75
109
132
47
84
113
Culbertson Roosevelt 36
32
28
May 20
May 06
Apr 26
Jun 08
May 22
May 14
Jun 27
Jun 07
May 31
Aug 10
Aug 27
Sep 06
Aug 28
Sep 10
Sep 19
Sep 15
Sep 25
Oct 01
107
134
149
80
110
128
53
87
106
Dillon
WMCE
Beaverhead 36
32
28
Jun 11
May 17
May 02
Jun 30
Jun 08
May 18
Jul 18
Jun 30
Jun 03
Aug 15
Aug 25
Sep 03
Aug 27
Sep 07
Sep 18
Sep 09
Sep 20
Oct 03
82
115
142
58
91
122
34
67
103
Ekalaka Carter 36
32
28
May 17
May 11
Apr 19
Jun 07
May 26
May 09
Jun 27
Jun 10
May 29
Aug 17
Aug 30
Sep 07
Sep 03
Sep 15
Sep 25
Sep 19
Oct 01
Oct 13
113
133
160
87
112
138
61
90
115
Fairfield Teton 36
32
28
May 23
May 07
Apr 23
Jun 09
May 20
May 06
Jun 26
Jun 03
May 19
Aug 28
Sep 04
Sep 15
Sep 09
Sep 20
Oct 03
Sep 21
Oct 07
Oct 21
111
146
172
91
122
149
71
99
126
Fort Benton Chouteau 36
32
28
May 17
May 09
Apr 24
Jun 08
May 21
May 07
Jun 29
Jun 03
May 20
Aug 26
Sep 02
Sep 08
Sep 07
Sep 14
Sep 24
Sep 20
Sep 25
Oct 10
114
132
160
91
114
139
68
97
119
Geraldine Chouteau 36
32
28
May 23
May 06
Apr 28
Jun 17
May 24
May 10
Jul 12
Jun 11
May 22
Aug 19
Sep 03
Sep 06
Sep 03
Sep 14
Sep 23
Sep 19
Sep 24
Oct 09
111
133
154
78
112
135
45
90
117
Glendive Dawson 36
32
28
May 01
Apr 21
Apr 14
May 14
May 05
Apr 27
May 28
May 19
May 09
Sep 04
Sep 10
Sep 21
Sep 18
Sep 27
Oct 06
Oct 02
Oct 14
Oct 21
144
168
181
126
145
162
107
121
142
Hamilton Ravalli 36
32
28
May 20
May 06
Apr 19
Jun 07
May 24
May 04
Jun 25
Jun 12
May 19
Aug 25
Sep 06
Sep 17
Sep 05
Sep 20
Oct 03
Sep 16
Oct 03
Oct 20
110
143
175
89
117
152
68
92
128
Hardin Big Horn 36
32
28
May 09
Apr 27
Apr 17
May 31
May 17
May 01
Jun 22
Jun 05
May 14
Aug 27
Sep 06
Sep 15
Sep 09
Sep 20
Oct 01
Sep 23
Oct 05
Oct 17
125
149
170
100
126
153
76
103
135
Harlem Blaine 36
32
28
May 17
May 06
Apr 23
Jun 05
May 23
May 08
Jun 24
Jun 08
May 24
Aug 18
Sep 02
Sep 09
Sep 04
Sep 15
Sep 24
Sep 22
Sep 28
Oct 08
119
137
157
91
114
138
63
91
118
Harlowton Wheatland 36
32
28
May 27
May 08
Apr 27
Jun 18
May 27
May 15
Jul 10
Jun 15
Jun 03
Aug 17
Aug 29
Sep 06
Aug 29
Sep 11
Sep 22
Sep 10
Sep 24
Oct 07
98
131
151
72
106
129
45
81
106
Helena
WSO
Lewis &
Clark
36
32
28
May 16
May 02
Apr 16
Jun 04
May 18
May 02
Jun 23
Jun 02
May 18
Aug 25
Sep 02
Sep 13
Sep 08
Sep 18
Sep 29
Sep 21
Oct 03
Oct 16
120
141
172
95
122
149
70
104
126
Hysham Treasure 36
32
28
May 12
Apr 29
Apr 16
May 28
May 16
Apr 30
Jun 13
Jun 01
May 14
Aug 28
Sep 04
Sep 15
Sep 09
Sep 18
Oct 02
Sep 21
Oct 02
Oct 18
122
143
173
103
124
154
84
106
135
Jordan Garfield 36
32
28
May 17
May 03
Apr 23
Jun 04
May 19
May 05
Jun 23
Jun 03
May 17
Aug 18
Aug 31
Sep 08
Sep 03
Sep 14
Sep 23
Sep 19
Sep 27
Oct 09
115
136
157
90
117
140
65
99
124
Kalispell Flathead 36
32
28
May 20
Apr 30
Apr 11
Jun 12
May 20
Apr 28
Jul 05
Jun 10
May 15
Aug 26
Sep 07
Sep 15
Sep 07
Sep 20
Oct 02
Sep 19
Oct 03
Oct 19
116
148
183
87
122
157
57
96
130
Lewistown
FAA AP
Fergus 36
32
28
May 22
May 10
Apr 25
Jun 15
May 24
May 10
Jul 10
Jun 07
May 26
Aug 20
Sep 01
Sep 09
Sep 03
Sep 18
Sep 25
Sep 17
Oct 04
Oct 12
106
137
156
79
116
137
51
94
118
Medicine
Lake 3 SE
Sheridan 36
32
28
May 09
May 02
Apr 23
May 28
May 18
May 11
Jun 16
Jun 03
May 29
Aug 18
Sep 01
Sep 07
Sep 05
Sep 18
Sep 24
Sep 23
Oct 05
Oct 11
124
148
160
99
123
136
74
98
111
Miles City
FAA AP
Custer 36
32
28
Apr 30
Apr 22
Apr 11
May 16
May 07
Apr 25
Jun 01
May 22
May 09
Sep 05
Sep 13
Sep 27
Sep 21
Sep 29
Oct 12
Oct 08
Oct 15
Oct 27
148
167
189
128
145
169
107
122
149
Plevna Fallon 36
32
28
May 15
May 05
Apr 25
Jun 04
May 21
May 09
Jun 24
Jun 06
May 23
Aug 18
Aug 26
Sep 07
Sep 03
Sep 14
Sep 24
Sep 18
Oct 03
Oct 12
113
141
158
90
116
137
67
90
117
Poplar Roosevelt 36
32
28
May 07
May 01
Apr 20
May 24
May 15
May 04
Jun 10
May 29
May 19
Aug 31
Sep 07
Sep 11
Sep 12
Sep 20
Sep 27
Sep 25
Oct 03
Oct 13
132
146
165
110
127
145
89
108
125
Roundup Musselshell 36
32
28
May 12
Apr 28
Apr 18
May 29
May 14
May 02
Jun 15
May 30
May 15
Aug 30
Sep 01
Sep 14
Sep 10
Sep 17
Sep 29
Sep 21
Oct 03
Oct 14
123
144
167
103
125
150
84
106
133
Scobey Daniels 36
32
28
May 12
May 02
Apr 20
May 29
May 18
May 07
Jun 14
Jun 03
May 24
Aug 18
Aug 29
Sep 06
Sep 06
Sep 15
Sep 26
Sep 26
Oct 01
Oct 15
124
141
167
100
119
140
76
98
114
Sidney Richland 36
32
28
May 10
May 04
Apr 22
May 31
May 17
May 07
Jun 21
May 29
May 21
Aug 26
Sep 06
Sep 12
Sep 08
Sep 19
Sep 26
Sep 22
Oct 01
Oct 09
122
142
159
99
125
141
76
107
124
Stanford 1
WNW
Judith
Basin
36
32
28
Jun 02
May 16
May 01
Jun 24
Jun 03
May 15
Jul 16
Jun 20
May 29
Aug 18
Aug 28
Sep 08
Aug 30
Sep 11
Sep 23
Sep 12
Sep 24
Oct 08
92
122
151
66
99
130
40
76
109
Terry Prairie 36
32
28
May 09
Apr 30
Apr 19
May 26
May 14
May 03
Jun 12
May 28
May 17
Aug 24
Sep 06
Sep 09
Sep 09
Sep 18
Sep 26
Sep 25
Sep 30
Oct 13
125
143
170
105
126
146
85
109
122
Thompson
Falls PH
Sanders 36
32
28
May 17
May 01
Apr 19
Jun 08
May 16
May 04
Jun 30
Jun 01
May 19
Aug 29
Sep 07
Sep 17
Sep 11
Sep 24
Oct 07
Sep 25
Oct 10
Oct 27
121
154
181
94
130
156
67
105
131
Townsend Broadwater 36
32
28
May 26
May 12
Apr 25
Jun 17
May 28
May 10
Jul 09
Jun 12
May 24
Aug 21
Aug 27
Sep 07
Sep 03
Sep 11
Sep 24
Sep 15
Sep 26
Oct 11
101
128
161
77
106
137
53
84
112
Vida McCone 36
32
28
May 08
Apr 28
Apr 16
May 21
May 14
May 03
Jun 04
May 30
May 19
Aug 28
Sep 05
Sep 15
Sep 12
Sep 20
Oct 01
Sep 27
Oct 05
Oct 17
135
149
170
113
129
151
91
108
131
Westby Sheridan 36
32
28
May 12
May 01
Apr 23
May 27
May 17
May 07
Jun 12
Jun 02
May 21
Aug 18
Sep 04
Sep 09
Sep 05
Sep 18
Sep 25
Sep 23
Oct 02
Oct 12
126
147
160
100
123
141
74
99
122
Wibaux Wibaux 36
32
28
May 23
May 05
Apr 25
Jun 17
May 23
May 12
Jul 11
Jun 09
May 29
Aug 12
Aug 21
Sep 06
Aug 28
Sep 08
Sep 23
Sep 12
Sep 26
Oct 10
100
134
157
72
108
133
43
81
108
1/ This table gives the probability of a later date in the spring and an earlier date in the fall of the occurrence of temperatures as cold, or colder, than 36, 32, and 28 degrees Fahrenheit and the probable length of the freeze-free period relative the same temperature threshold.
[Top of Page]