I found this clickable map that I thought might be of some interest.
High and low temps, precipitation and snowfall averaged over 29 years.
Also, Daily % chance of precip, sunhine. Wind speeds.

http://www.cdc.noaa.gov/USclimate/states.fast.html

Check out Mt. Washington NH! AVERAGE low in the "dog days of summer" is around 40 degrees with average low extremes down to 30! Those are just averages.

In the anomalies, I see where it dipped to sub-zero degrees a few times throughout the years during this time period with the lowest, a chilly -5.
The good news is the wind average is about 25 to 30 mph during this time.

Be prepared!