Children's Museum of Manhattan (83rd and Broadway) is absolutely essential when weather turns bad. $14 kids, $18 adults, and the interactive exhibits will keep them occupied for 3+ hours. Close to the 1 train at 86th Street for easy subway access.

Also great: New York Transit Museum in Brooklyn (subway-themed exhibits kids love), and Barnes & Noble locations with large children's sections where they can browse books while you grab coffee and decompress.

Most NYC playgrounds have some covered areas, but having solid indoor options prevents complete meltdowns during extended rainy periods. Trust me on this one.