Saipan motorists have been filling up as Tropical Storm Bolaven approaches. Photo: Mark Rabago
An update at about 7:30AM local time said the storm's maximum sustained wind speeds were 112 kilometres per hour.
Bolaven is forecast to intensify, possibly becoming a typhoon.
Paul Stanko, a senior meteorologist at the US National Weather Service Guam, said on Tuesday morning the system is expected to reach the Northern Mariana Islands (CNMI) at about 7pm Tuesday, local time.
Stanko said the storm would likely only reach category one strength as it passes through the Marianas - not category two which was previously forecast.
He said the storm has had trouble getting stronger.
"Tropical storm Bolaven has been intensifying slowly, which has been good news for us; we were worried if it were to be rapidly intensifying," Stanko said.
"The current track has it going between Rota and Tinian, and so if we get really blessed all the typhoon force winds will be over the ocean."
A typhoon warning remains in effect for Rota, Tinian and Saipan, with a tropical storm warning and typhoon watch for Guam.
A tropical storm watch remains in effect for Agrihan, Pagan, Alamagan and Anatahan.
"A direct hit is pretty unlikely on Guam but of course we'll be getting some of the tropical storm force winds from the south," Stanko said.
Stanko said up to 300 millimetres of rain was also forecast for the Marianas in the 24 hours from Tuesday morning.
He said people living in corrugated roof homes needed to prepare the most for the storm, while people living in concrete homes should be fine.
Tropical storm Bolaven is developing slower than expected. As of Tuesday morning a typhoon warning was in effect for Rota, Tinian and Saipan, with a tropical storm warning and typhoon watch for Guam. 10 October 2023 Photo: NOAA
Meanwhile, the Northern Mariana Islands declared typhoon 'condition one' at 5am local time.
That level means typhoon force winds of about 120kph or more are expected, with damaging storm force winds of just over 60kph arriving within 12 hours.
Residents of Saipan, Tinian, and Rota have been told to prepare for a category two typhoon, which would bring winds of 154 to 177kph.
Public schools in the Northern Mariana Islands were closed on Tuesday because of the storm, and most will be used as shelters.
The Northern Marianas Technical Institute have also suspended classes on Tuesday and Wednesday.
Shelters have been activated in the CNMI - all were opened at 6pm on Monday apart from Rota's shelter which was to open at 7am Tuesday.
A spokesperson for the Governor's Office has asked residents who need shelter to bring their own bedding, food and drinks.
Governor Arnold Palacios asked residents to stay indoors, unless for emergency purposes.
He said to stay away from windows and glass doors and be sure important documents like birth certificates are secured.
On Sunday a price freeze was put in place, which includes fuel and food, when a state of significant emergency was declared for the CNMI.