The state-run WAM news agency called the rain Tuesday "a historic weather event" that surpassed "anything documented since the start of data collection in 1949" - before the discovery of crude oil in the energy-rich region then part of a British protectorate known as the Trucial States.
Rain also fell in Bahrain, Oman, Qatar and Saudi Arabia.
However, the rains were acute across the UAE.
One possible contributor may have been cloud seeding - in which small planes operated by the government fly through clouds burning special salt flares.
Those flares can increase precipitation.
Several reports quoted meteorologists at the National Centre for Meteorology as saying they flew six or seven cloud-seeding flights before the rains.
Dubai airport says flooding has affected flights as aircraft crews could not reach the airfield. (EPA PHOTO)
Flight-tracking data analysed by the Associated Press showed one aircraft affiliated with the UAE's cloud-seeding efforts flew around the country on Monday.
The National, an English-language state-linked newspaper in Abu Dhabi, quoted an anonymous official at the centre on Wednesday as saying no cloud seeding took place on Tuesday, without acknowledging any earlier flights.
The UAE, which heavily relies on energy-hungry desalination plants to provide water, conducts cloud seeding in part to increase its dwindling, limited groundwater.
The rains began late on Monday, soaking the sands and roadways of Dubai with 20mm of rain, according to meteorological data collected at Dubai International Airport.
The storms intensified about 9am on Tuesday and continued throughout the day, dumping more rain and hail onto the overwhelmed city.
By the end of Tuesday, more than 142mm of rainfall had soaked Dubai over 24 hours.
In an average year, 94.7mm of rain falls at Dubai International Airport, a hub for the long-haul carrier Emirates.
At the airport, standing water lapped on taxiways as aircraft landed.
Arrivals were halted on Tuesday night, and passengers struggled to reach terminals through the floodwater covering surrounding roads.
One couple, who spoke to the AP on condition of anonymity to speak freely in a country with strict laws that criminalise critical speech, called the situation at the airport "absolute carnage".
"You cannot get a taxi. There's people sleeping in the Metro station. There's people sleeping in the airport," the man said on Wednesday.
They ended up getting a taxi to near their home 30km away but floodwater on the road stopped them.
A bystander helped them over a highway barrier with their carry-on luggage, the bottles of gin they picked up from duty-free clinking away.
Dubai International Airport acknowledged on Wednesday morning that the flooding had left "limited transportation options" and affected flights as aircraft crews could not reach the airfield.
"Recovery will take some time," the airport said on the social platform X.
Emirates said the airline had halted check-in for passengers departing from Dubai itself from 8am until midnight on Wednesday as it tried to clear the airport of transit passengers - many of whom had been sleeping where they could in its cavernous terminals.
Passengers on FlyDubai, Emirates' low-cost sister airline, also faced disruptions.
Paul Griffiths, the airport's CEO, acknowledged continued issues with flooding on Wednesday morning, saying every place an aircraft could be safely parked was taken.
Some aircraft had been diverted to Al Maktoum International Airport at Dubai World Central, the city-state's second airfield.
"It remains an incredibly challenging time. In living memory, I don't think anyone has ever seen conditions like it," Griffiths told the state-owned talk radio station Dubai Eye.
"We are in uncharted territory, but I can assure everyone we are working as hard as we possibly can to make sure our customers and staff are looked after."
