The best example that illustrates a sensitive period is
letter b, where the child tries to learn in speaking a second language because
this is considered to be a sensitive period in which is the period for a
development of new opportunities that a child could learn in which learning to
speak a second language is considered to be a sensitive period.
A cold front does count as weather, if you're looking for more info on cold fronts and warm fronts visit the site below.
http://www.weatherquestions.com/What_are_fronts.htm