There's a treatment of this subject in 'The American Practical Navigator'
('Bowditch').
Wave height and period are a function of wind strength and the time and
distance that the wind has had to build them up. If the fetch is across a
large body of water, waves will be higher. If the wind has only recently
risen, the waves will be flatter. Rain smooths small waves further. Icing
smooths things, too. If there's been a large wind shift, waves will be
irregular. Shallow water makes makes waves shorter and steeper.

wrote:

Hi,

I have a boat on Lake Lanier in GA. The other morning I took it out,
and the overall wave action appeared to be different than usual.
It was a flat calm day, except when a passing boat produced some
waves. Most of the time the waves seem to be sort of peaked and
a bit sharp, but on this morning they were more rounded and flatter.
The first boat I noticed it from, I thought it might be simply due to
the shape of the boat itself. But after a while I noticed it was true of
all of them...which was cool with me because it meant I could go
faster without getting tossed in the air too much. It still made me
wonder *why* though. Could it have something to do with what
creates high and low tides, and/or why sometimes when you dig
a hole you seem to have more dirt than you took out and sometimes
you seem to have less? If so, is there a way to predict when waves
will tend to be sharper and when they will tend to be flatter, like
people can predict high and low tides?