Residents in the Northern Marianas are bracing for Typhoon Hagibis, which is expected to bring winds of up to 170 kilometres an hour (105 mph).
The tropical storm has been upgraded to typhoon status.
Based on the ongoing rapid intensification, the US National Weather Service said Hagibis' passage through the CNMI could be as a Category 3 or 4 typhoon.
Super Typhoon Yutu, which struck the islands in October 2018, was a Category 5.
As currently forecast, Hagibis is still expected to pass north of Saipan late tonight or early Tuesday morning, near Anatahan Island at least as a Category 2 Typhoon.
From this point on, weather conditions across the CNMI will deteriorate. Seas and surf are building across the region and will soon become hazardous. Heavy rains and gusty winds have been observed across the CNMI the last few hours. A Flash Flood Watch remains in effect for Saipan, Tinian, and Rota.
Hagibis' rapid intensification has forced several carriers flying to Saipan to cancel flights. According to the Commonwealth Ports Authority the cancellations include flights from Asiana Airlines, Jeju Air, United Airlines, Sichuan Airlines, and T'Way.
Tinian-based Star Marianas Air has also grounded all passenger flights in and out of the Saipan, Tinian, and Rota airports.
Apart from government offices and public schools being closed, a number of businesses have shut down today in anticipation of the year's biggest storm to date.
RNZ Pacific's correspondent reports that on Saipan, there have been scenes of motorists frantically filling their vehicles, residents buying extra food and emergency supplies, long queues at water refilling stations, and people boarding up windows.
There are already people using the emergency shelters on the island.
The CNMI government has activated four schools - Koblerville Elementary School, Kagman High School, Marianas High School, and Tinian Elementary School - for use as emergency shelters.
Just on a year ago, Saipan and Tinian were hit by a huge typhoon, Yutu, which caused widespread damage from which they are still struggling to recover.