The first year that I planted a garden here in Shelby, Corinne Merhar warned me not to put out the tomato plants before Memorial Day.  I had to learn the hard way. You're not "safe" from frost in Shelby until the end of May.  A few years later I had the biggest most beautiful tomato plants I had ever grown....until a freak August snowstorm blew through. 

 Gardening can be a challenge in northcentral Montana.

The MSU Extension service has a ton of information available to help gardeners plan and raise a bountiful crop, including a chart that shows the average dates of the last spring frost and first fall frost, which determine the number of days in a "growing season".  The season can vary widely, from an average of 139 days in Great Falls to just 93 days in Browning. I was surprised to see that Dunkirk- just 10 miles east of Shelby- has a 120 day growing season, compared to Shelby's 110 days. And Gold Butte's season is eight days longer than Shelby's.

Here are the dates various locations in the Golden Triangle. you can plant and harvest outside these dates, of course, but you'll need to monitor the weather forecasts and take extra care to protect your garden from cold.

Location Last Frost First Frost Growing Days
Augusta 29-May 10-Sep 104
Babb 29-May 8-Sep 102
Big Sandy 15-May 20-Sep 128
Browning 6-Jun 7-Sep 93
Carter 20-May 15-Sep 118
Chester 25-May 7-Sep 105
Choteau 26-May 15-Sep 112
Conrad 21-May 19-Sep 121
Cut Bank 23-May 17-Sep 117
Dunkirk 22-May 19-Sep 120
Fairfield 19-May 20-Sep 124
Ft Benton 11-May 25-Sep 137
Gold Butte 24-May 19-Sep 118
Great Falls 9-May 25-Sep 139
Havre 11-May 22-Sep 134
Lothair 15-May 19-Sep 127
Shelby 27-May 14-Sep 110
Sun River 27-May 27-Sep 117
Valier 17-May 23-Sep 129