If it is hot then the person/people communicating may sweat which comes across as being nervous.If it is too hot then the people/person may feel a little dehydrated and so not have that energy or moisture in there mouth to speak well.
Or it being to cold could see people put hands in pockets to warm themselves up which comes across as rather rude. Also when it it cold words can become stuttered as the jaw shivers
Hope that helped, not too sure tho :)