dry, hurricane, monsoon, rainy, wet
In this climate there are no real changes of temperature, just a wet and a dry season.

summer, winter, etc.

be in, come into (esp. AmE)
Melons are in season right now.

be out of
Lobster's out of season right now.

holiday (= when people are on holiday/vacation), tourist
high (esp. BrE), peak
The resort gets overcrowded in peak season.

low, off
The hotel is almost empty in the off season.

coming, forthcoming (BrE), upcoming (esp. AmE)
breeding, mating, nesting
growing, harvest, planting
close (BrE), closed
It is illegal to fish for salmon during the closed season.

open (often figurative)
The media have declared open season on the congressman and his private life.

political (esp. AmE)
campaign, election, primary (all AmE)
The Senator has led in the polls for most of the primary season.

conference (BrE)
The party conference season gets under way this week.

silly (BrE)
Fleet Street's silly season is upon us.

flu (esp. AmE)
This year's flu season has been relatively mild.

movie, TV (both esp. AmE)
Christmas, festive (BrE), holiday (= the time including Christmas, Hanukkah and New Year)
Best wishes for the festive season!
I wished everyone a very happy holiday season.

panto (informal), pantomime (both BrE)

the height of the season

baseball, cricket, football, hunting, racing, etc.
championship, league
Decker played nine major league seasons. (AmE)

junior, senior, sophomore (all AmE)
debut (esp. BrE), rookie (AmE)
inaugural
The Denver Broncos' inaugural season was 1960.

regular (AmE)
The Patriots won their last 12 games in the regular season.

full
He played a full season for West Ham.

difficult, hard, tough (all esp. BrE)
It was the final race of a hard season.

outstanding, successful, undefeated (esp. AmE), winning (esp. AmE)
disappointing, disastrous, poor (esp. BrE)
coming, forthcoming (BrE), upcoming (esp. AmE)
He is busily preparing for the coming season.

close (BrE), off (AmE)
The team trained hard during the close/off season.

consecutive, successive
Our team won the trophy for the second successive season.

begin, open, start
We opened the season with five straight losses.

end, finish
enter
He entered the season with 173 wins.

begin, kick off (esp. BrE), start
The new Premiership season kicks off on August 17.

end

ticket
season ticket holders

opener (AmE)
They played against the Celtics in the season opener.