Open Question: Freezing while hiking?

Hi, I usually like to hike, but the last two times i went hiking i started getting cold, like really cold. Others were just fine wearing t-shirts, some bear no t-shirt and they said it was like 80 something degrees outside, while i was feelign it was like a night in fall or around 50 degrees and i was wearing a sweater and that didnt seem to help either. Any way my question, i guess, is what wrong with me?

Source:
http://answers.yahoo.com/question/index?qid=20110729190452AAL8JCY

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