Here in the Puget Sound area most of the sea-run cutthroat spawn between early Janaury and the end of May. Typically the peak spawning activity would be in mid to late March. Depending on conditions there can be a shift of a week or two in the "spawning curve".

As an side the spawning usually takes place in small low land streams. Those streams are typically low-gradient and on many a man can step or jump across the stream.

Tight lines
Curt