I was reviewing some data-sets at the Western Regional Climate Center (http://www.wrcc.dri.edu) and saw that had some data for Miles. Here's a sample of what they have available, if anyone is interested:

MILES CITY, MONTANA (245685) Period of Record Monthly Climate Summary
Period of Record: 1/ 1/1893 to 7/31/1982
http://www.wrcc.dri.edu/c....pl?mt5685

The menu at that page also gives similar data for different time frames.