The hurricane center also expects the coast of Nicaragua and Honduras will see a life-threatening storm surge as much as 10 to 15 feet above normal tide levels, with large and risky waves near the coast.
This year's Atlantic hurricane season is the busiest on record, with Iota becoming the 30 named storm and 13 hurricane so far in 2020.
On the official NHC forecast track, the core of Iota will make landfall within the hurricane warning area in northeastern Nicaragua tonight and will dissipate over central America by Wednesday.
"Rapid strengthening is expected during the next 36 hours, and Iota is forecast to be an extremely risky category 4 hurricane when it approaches Central America", the Miami-based NHC said.
A tropical wave could develop in a few days in the same area where Iota is now
As of 10am EST (15:00 GMT), Hurricane Iota was about 335 miles (539 km) off the Nicaraguan-Honduran coast, packing maximum sustained winds of 90 miles per hour (145 km/h), according to the US National Hurricane Center (NHC).
National Public Radio reported that an estimated 63,500 people in Honduras and 1,500 people in Nicaragua evacuated or relocated ahead of Iota's landfall.
As the storm moves inland, winds will rapidly diminish.
In Bilwi, where Eta made landfall on November 3, residents were fearful that their homes might not stand up to the latest storm so soon after weathering the last one, The Associated Press reports. Local television showed people being evacuated in wooden boats, carrying young children as well as dogs and chickens. Then it meandered across Cuba, the Florida Keys and around the Gulf of Mexico before slogging ashore again near Cedar Key, Florida, and dashing across Florida and the Carolinas.More news: European activist files complaints against Apple's tracking tool
So many, that by October, with the arrival of tropical storm Wilfred in the eastern Atlantic, meteorologists had already used every name on the season's list, causing them to move to the Greek alphabet for names, which had not been necessary since 2005.
Iota was forecast to drop 200-400 millimetres of rain in northern Nicaragua, Honduras, Guatemala and southern Belize, with as much as 750 millimetres in isolated spots.
Iota could also bring heavy rainfall and flooding to portions of Haiti and Jamaica, with possible landslides, forecasters said.
"Hurricane-force winds should begin in a few hours, with landfall expected this evening".More news: The Trailer for Steven Soderbergh's Let Them All Talk
National Oceanic and Atmospheric Administration climate and hurricane scientists studied the effect and found "a lot of that has to do with human-caused climate change".
"Category 5 Hurricane #Iota is getting closer to Nicaragua", tweeted the NHC.
There have been no other Novembers on record with two major hurricanes.More news: Environment Canada issues wind warning for Toronto