Well the simple kind that is...Haiku!
http://en.wikipedia.org/wiki/Haiku - For those who don't know.
Basically it consists of three lines. The first having 5 syllables, second having 7 and the third having 5 again.
Aka I wrote this one while near the River Thames in London in the afternoon:
The River Flows Down
And the Twilight is Setting
Louder is the Wind.
Usually you write about seasons without hinting it or something you saw that inspired you. Right now it is raining over here. Perhaps if it is the same for you then you can write one to do with the gustily rain
Have a try fellow poets D: