Thanks to the USGA's new ticketing policy, plans are already in place for a Sunday rainout. If less than 90 minutes of golf are played Sunday, fans with Sunday tickets can come back Monday. Here's the USGA's release from Sunday morning:

For play on Monday (conclusion of Round 4 and Playoff, if necessary), spectators holding Thursday or Monday tickets will be admitted to the course through the admission gates. 

If less than 90 minutes of golf are played today, Sunday tickets will also be honored on Monday.

On Monday, Thursday ticket holders who have lost or misplaced their Thursday ticket should report to one of the Will Call facilities located at Bethpage State Park.

For individuals who purchased their tickets by mail or online well in advance of the championship, Will Call will verify their purchase with available records.

Individuals who purchased tickets at the pre-championship on-site sale (June 11-14) will need to show their receipt at Will Call.