making a conjecture urgent help!

[magmagod]

I posted an attachment scan from the book itself...with the question and everything...i want help with the first question which asks for a conjecture (hypothesis) about which city has the greatest rate of increase in mean daily temperature. This is what i have done so far:

isolated the times of increase which were from negative 13.7 to 18.9 and -4.7 to 22.6..then i took the median by adding them and dividing by 182 days...is what im doing even right?? If anybody can help me..i would appreciate it..