The storm was located about 545 km (340 miles) from Kingston, Jamaica, the NHC said.
“Iota is expected to reach or near the force majeure hurricane as it approaches Central America,” the agency said in its statement.
Guatemalan President Alejandro Giammattei said on Saturday that he had ordered evacuations in areas that should be affected by the impending storm.
“We are concerned about the Alta Verapaz and Quiche area. We believe these are the areas where we could have the greatest impact, ”said Giammattei. “We hope that God helps us.”
In Honduras, President Juan Orlando Hernandez also urged those on their way to Iota to evacuate to the nearest shelters. “Iota will once again put our lives and our economy at risk,” he said.
The region is still recovering after Category 4 hurricane Eta struck earlier this month, killing at least 120 people, according to the Reuters news agency tally.
Heavy rains led to deadly flash floods and landslides in several countries.
On Saturday morning, Guatemalan authorities said a mudslide had buried 10 people in the state of Chiquimula, near the border with Honduras. Rescuers said they saved two people and recovered three bodies, while five others are still missing.
The region of Alta Verapaz in Guatemala was particularly affected by the Eta, as a mountain partially collapsed in the village of Queja, killing and burying dozens of people alive.
Rescue operations in Honduras and Guatemala have been slowed by the destruction of roads and bridges, forcing authorities to enlist the military and use helicopters and speedboats to rescue people stranded atop their homes.
Iota is already a record system, being the 30th named storm of this year’s extraordinarily busy Atlantic hurricane season.
Such activity has drawn attention to climate change, which scientists say is causing wetter, stronger and more destructive storms.
We are concerned about the Alta Verapaz and Quiche area. We believe these are the areas where we could have the greatest impact. We hope God helps us
The NHC said the storm could lead to life-threatening flash floods and cause rivers to burst in parts of Haiti, Jamaica and Central America through Wednesday.
Residents of the community of Cruz de Valencia, in northwestern Honduras, have already started to evacuate.
“We have to get out, we have to save our lives,” resident Erick Gomez told Reuters news agency.
Gomez said he only survived the flooding from the last hurricane by hanging onto a tree to avoid being swept away by the rushing waters.
“We are afraid of what we just suffered with Eta, and we don’t want to do the same again,” he added.