If you click the Weather tab you can find a link to a climate chart for Miles City on the lower right hand corner of the page. Forsyth is fairly close so I assume it would be similar.
Looks like the temperature could range from from about 100° to 10°. Normal daytime highs being about 65°, normal nighttime lows about 40°.
Of course, normal seldom happens, and there is a saying in Montana... if you don't like the weather, just wait 15 minutes and it will change.
[This message has been edited by Larry Antram (edited 2/15/2001).]