Recent Weather Data	Normals (Averages)	Records (Extremes)	Long-Range Predictions	Misc. Climate Data
Climate Normals (Long-Term Averages)

See Graphs Like These:

They show the actual daily highs and lows, as well as the normals and records (extremes).

Get Daily Normals (output to a new/separate page):
All Maxes Means Mins Precip Snow HDD CDD	One Day One Month All Year Both Sites Harrisburg Williamsport January February March April May June July August September October November December November 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 24 Select Ouput Type:

Daily Normals for November 24th for Both Sites.
Town	Date MM-DD	Normal Max	Normal Mean	Normal Min	Normal Precip	Normal Snowfall	Normal HDDs	Normal CDDs
Williamsport	11-24	45	38	30	0.12	0.1	27	0
Harrisburg	11-24	49	42	34	0.12	0.1	23	0

See the TEXT List of All IPT and MDT Daily Normals (experimental)
CLIM81: Monthly Station Normals of Temperature, Precipitation, and Heating and Cooling Degree Days (1971 - 2000) for all of Pennsylvania (pdf document, 1.28Mb).
Pennsylvania Wind Rose Downloads (gifs) from NCDC (ftp site).

Snowfall Tidbits:
Seasonal Co-Op Snowfall Maps

Local Growing Season (Frost & Freeze Dates):

The BEGINNING of the growing season is set by the average date of the last freeze in spring, and normally happens during very late April to mid May in Central PA.
The NWS will then issue Frost Advisories and Freeze Warnings, when appropriate, until the end of the growing season which is the ACTUAL first (widespread) freeze in the autumn. See a map of the Average Date of the First Freeze in Autumn.