Driest Date On Average
April 1
0.02
No April Fool's joke right there!

Wettest Date On Average
May 29
0.40
Seems like around Memorial Day tends to be wet.
Coldest Date On Average (Daily Temperature Average Of Low and Highs)
December 25
49.05°F
This past Christmas was very warm. Usually Christmas is quite cold.

Warmest Date On Average (Daily Temperature Average Of Low and Highs)
July 30
84.62°F
End of July to early August is very hot.
Coldest Lowest Temperature Date On Average (Lowest Temperature Of Day)
December 25
38.76°F
Again, Christmas has the lowest temperature on average on any given date. Good reason that Christmas is cold as it should be.

Warmest Lowest Temperature Date On Average (Lowest Temperature Of Day)
August 7
74.73°F
Again, late July to early August is very hot.
Coldest Highest Temperature Date On Average (Highest Temperature Of Day)
January 2
59.05°F
It seems much cooler in late December to early January.
Warmest Highest Temperature Date On Average (Highest Temperature Of Day)
August 20
95.19°F
Interestingly, late August is very hot in terms of high temperatures. Many record highs happen in mid to late August.
Got the data from this link.
http://www.ncdc.noaa.gov/cdo-web/search?datasetid=GHCND