The Rules of a Cinquain poem:
They have 2 syllables in the first line, 4 in the second, 6 in the third, 8 in the fourth line, and just 2 in the last line. Cinquains do not need to rhyme, but you can include rhymes if you want to.

Today
is the day of
neon greens and blues, of
waterguns and ‘Time in!’ and
running through sprinklers in
flip flops because park rules say
everyone must wear shoes,
and, occasionally, a scraped knee from
hydroplaning.