+0
Does 'a long rainy term' sound natural as 'a long rainy season'?
+0
It is not natural.
You can say "a long rainy spell"
+0
Hi Taka

I agree wholeheartedly with AlpheccaStars that "term" would be an unnatural replacement for the word "season" in your sentence (and I might go so far as to say it's just plain wrong).

A term can be arranged or contractually fixed, for example. It might also refer to a prearranged ending date. It is also possible to use the word in connection with a pregnancy which lasts for the full ("standard") amount of time (i.e. a pregnancy in which the baby is not born prematurely).
You can't arrange, schedule or predetermine the precise ending date of a rainy season, much less a long one.

http://www.bartleby.com/61/58/T0115800.html
http://dictionary.cambridge.org/define.asp?key=81991&dict=CALD
Students: Are you brave enough to let our tutors analyse your pronunciation?
Comments  
Why do you think it's unnatural? What do you think the meaning of 'term' is?
 Yankee's reply was promoted to an answer.
Students: We have free audio pronunciation exercises.