The weekends are rush hours for subway crooks.

Extra cops have been dispatched underground to combat a dramatic spike in subway felonies, which rose 29.6 percent last month compared with August, 2011.

Nearly half of all crime underground — 46 percent — happens on Friday, Saturday or Sunday, NYPD Assistant Chief Owen Monaghan said yesterday at an MTA committee meeting.

The flood of cops includes undercover decoys looking to catch crooks, and officers handing out fliers to warn straphangers.

Most of the crimes are the thefts of pricey smartphones and other electronic gadgets.

The NYPD made 25.2 percent fewer arrests last month than in the same period last year.