July 4th Climatology
Looking back at records dating to 1873 for the Twin Cities, the average high and average low for Independence Day are 82.4 degrees F and average low of 62.6, respectively. 2012 came in as the warmest July 4th on record at 101 degrees, this was a part of an extremely warm early July. 1967 recorded the lowest high temperature at 58 degrees, which was the last time the high temperature has dipped below 70 degrees.
Although recent July 4th's tend to have warm and mostly dry, Mark Seely mentions on the June 28th 2013 WeatherTalk that it is the rainiest holiday in Minnesota looking back to 1891. The heaviest rainfall occurred in 1900, a year that saw 2.27 inches of rain over Independence day. The most recent washout occured in 1995, the Twin Cities reported 0.24 inches from 6:00-8:00 PM, with a brief shower at Noon. This has been the lone rain event to disrupt July 4th events in the Twin Cities for the past 50 years. Furthermore, in the Twin Cities area, 64% of years dating back to 1871 have seen less than .10 inches of rainfall on July 4th.
The National Weather Service Office for Chanhassen has a story on their website.
The raw information for the 4th of July climate in the Twin Cities can be found here