The climate in Pennsylvania is cold in the winter and warm in the summer
The average winter weather is anything ranging below 40 degrees
The summer weather is a long lasting thing, bringing humid heat to the southeast. The temp can be 70 and higher in most places.
The fall weather is rather cooler in the morning and slowly gets warmer throughout the day. The typical weather is 40 through 70. The coldest month is January and the warmest month is June.
I recommend wearing a coat and heavy clothes in the winter and shorts and a tee shirt in the spring and summer
The Temperate Forests of Pennsylvania 