From the USPS Website:
USPS Service Alerts
Last updated Aug. 28, 2017, 5 p.m. ET
Tropical Storm Harvey
Tropical Storm Harvey has stalled over southeast Texas where extreme rainfall has caused catastrophic flooding across the Houston metro area. Days of drenching downpours are ahead, along with the potential for tornadoes and lingering coastal flooding. New mandatory and voluntary evacuations have been ordered southwest of downtown Houston.
Postal operations have been impacted in the region. Check “Service disruption alerts” or “Is my Post Office open” under “Residential customers” below for the latest information.
USPS Service Alerts provide information to consumers, small businesses and business mailers about postal facility service disruptions due to weather-related and other natural disasters or events. Service alerts are done in near real time.
Residential customers and small businesses can use this website to learn if mail is being delivered, or if their Post Offices are open. Business mailers are provided more detailed information about USPS mail processing facilities, and the operating status of postal delivery units.