Cyclone Amphan made landfall last night (AEST) near the India-Bangladesh border with winds gusting up to 185 kilometres per hour, approximately a category three on Australia's cyclone scale.
The system has weakened as it moves inland, but at least 82 people have been reported dead.
It is the latest massive storm to hit the Bay of Bengal, a region notorious for producing cyclones that have claimed hundreds of thousands of lives.
The world's deadliest cyclone
The Bay of Bengal was the setting for the deadliest weather event on modern record, Cyclone Bhola.
On November 12, 1970, the storm made landfall over the Bhola region of what was East Pakistan (now Bangladesh).
Most reports suggest 300,000 people died; some estimates put the toll as high as 600,000.
Cyclone Bhola coincided with a lunar high tide, compounding the storm surge that inundated the low-lying region and swept away thousands of people.
Late warnings and complacency resulting from a weaker cyclone in the months before likely added to the death toll.
Many killer cyclones have originated in the Bay of Bengal, with one that hit Bangladesh in 1991 resulting in an estimated 138,000 deaths.
What makes the Bay of Bengal so deadly?
Greg Holland, senior scientist emeritus at the National Centre for Atmospheric Research in Boulder, Colorado, said it was not necessarily that there were a large number of storms in the region, but the geography.
With India to the west, Myanmar and Malaysia to the east and Bangladesh in the north, the Bay of Bengal was ocean surrounded by land, he said.
"Basically, any cyclone coming up and going north through the Bay of Bengal has got a good chance of hitting land somewhere."
Then there is the region's population density.
If a cyclone were to hit anywhere between Darwin and Port Hedland, there is a pretty low chance of large numbers of people being directly affected.
"A cyclone hits anywhere in the Bay of Bengal, and it's going to be a lot of people affected," Dr Holland said.
Getting all those people out of harm's way is also a struggle — three million people were evacuated in preparation for Cyclone Amphan.
"India has a quite well coordinated program of evacuation and the people do move, they get up and they leave," Dr Holland said.
"In India you can do that because people can go inland and basically get away from the worst of it."
But Bangladesh was difficult to evacuate, he said, for both socioeconomic and geographical reasons.
The majority of the country, one of the world's most densely populated, is less than nine metres above sea level, making it incredibly vulnerable to storm surges.
"You have to go a very long way inland in the Ganges delta area to get away from any aspects of tropical cyclones," Dr Holland said.
How have things gotten better?
Changes undertaken in Bangladesh since the 1990s count among the great victories in emergency management.
As evacuating to higher ground is not an option for many citizens, the country has developed an innovative approach of going vertically, according to Dr Holland.
"They have concrete towers which can be used as community facilities, schools, in the good times, but people can go in there and climb up and get above the storm surge in the bad times," he said.
Warnings, communications, protective embankments and recovery support have also improved.
"Nowadays it's still bad; it's not unusual to get 5,000 people dying when a major cyclone comes to shore, but 5,000 is a heck of a lot better than 300,000," Dr Holland said.
The effectiveness of the warnings, evacuations and shelters this time around, on top of COVID-19, will become apparent in the days and weeks ahead.ABC