Find a roost! Somewhere within a mile of the ocean look for an isolated clump of trees that sticks out like a sore thumb. Monarchs are attracted to such clumps (if they exist in Salem).
There are 1000's on the south coast of Maine right now: http://www.learner.org/jnorth/sightings ... 1347818633
Might be a record high year for the coast of New England. And a record low year for the upper Midwest because the predators of monarch eggs and caterpillars decimated the monarch population.