Generally speaking Pennsylvania is not prone to tornados. You are coming after the more rainy season, but that can just depend. Almost every building here it seems has air conditioning, public ones anyway. I have been to Germany and other places in Europe and always found it weird that so many places do not. They will give you ice in your drink, unless you say otherwise. The water will not be fizzy, unless you ask for seltzer water.
I am a couple of hours from Pittsburgh in Northern Virginia and the weather is a pleasant 80F and clear lately. Rain has been coming in about once a week, but not for days on end for awhile now.
Flying across the Atlantic is fun, but exhausting. Try to get an aisle seat. If you are flying Lufthansa, they are usually really nice.
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