The National Weather Service operates an automated observation station at nearby Bear Mountain (elevation 5,400 feet). This weather station gives hourly updates on temperature, precipitation, snow depth, and more.
The above mentioned link no longer works.
Some of the directions listed above are out-of-date. The best place to go for updated information about Scotchman Peak is the Friends of Scotchman Peaks Wilderness website - http://www.scotchmanpeaks.org/hiking/self-styled-hikes/scotchman-peaks-trail-65/. It's a wonderful hike!