When the Ultimate Fighting Championship (UFC) heads to the White House on Sunday for the first-ever professional sporting event at the US presidential residence, many of those in attendance will be keeping their eyes on the sky.
About 4,300 people are expected at the invite-only mixed martial arts event on the South Lawn, with another 85,000 expected at a nearby fan zone.
A lawsuit failed to halt the event, but hot weather and thunderstorms expected to sweep across the city on Sunday could dampen the spectacle, or send some of those thousands rushing for cover.
The action is set to start at 20:00 EDT (midnight GMT, 01:00 BST), during a window when the National Weather Service expects the air to thicken with humidity exceeding 70% and the temperature to hover around 80F (27C).
The agency has warned "damaging thunderstorms" may shake the region in the evening, and it forecasts a 70% chance of rain that could drop as much as half an inch of water on Washington.
The event coincides with President Donald Trump's 80th birthday, which is also Flag Day, and is part of celebrations for America's 250th anniversary.
The seven-bout card was arranged between Trump and his longstanding friend Dana White, UFC president.
The UFC spent about $60m (£45m) on the event, including $700,000 for grass repairs afterwards on a lawn that hosts the annual Easter Egg Roll.
The centrepiece is the "Claw" - a 92ft high metal structure that looms over the octagon and many of the seats. It weighs 600 tonnes.
A total of 14 fighters will compete in back-to-back fights, ending with the main card between Georgian-Spanish lightweight Ilia Topuria and American Justin Gaethje.
It will be screened exclusively on Paramount+, which is run by Trump ally David Ellison. Last year, UFC signed a $7.7bn deal with the Netflix rival streaming service.
The ultimate winner may be UFC - making it to the White House is a fist-pumping brand boost for a sport that was once shunned by sponsors and venues and denounced as "human cockfighting" by a US senator.
Administration officials - including Trump - have repeatedly praised the event, with the president referring to it as "the greatest show on Earth" and comparing the Claw to the Eiffel Tower in Paris.
Secretary of State Marco Rubio this week lauded the UFC as the "definition of American soft diplomatic power" and announced the launch of a private-public partnership to use the UFC as a diplomatic tool.
Just days before the fight, a lawsuit was filed on behalf of two Virginia residents - a Vietnam veteran and a local civic activist - to try halt the event.
The legal action, filed by the Public Integrity Project, a self-described anti-corruption law firm in Washington, argued the event was "deeply corrupt".
It cited a lack of approvals for the weigh-in at the nearby Lincoln Memorial and President Trump's close personal and financial ties with Dana White and the UFC.
But on Friday, a judge denied an emergency injunction to stop the fight - a ruling welcomed by the White House, which described the lawsuit as "frivolous".
A Reuters/Ipsos poll released on Friday, however, suggested many Americans were sceptical of the event.
The survey found that only 16% of Americans believed it appropriate to hold the UFC fight at the White House, compared to 46% who thought it inappropriate.
Only about a third of Republicans approved of the plan.
The UFC fight is one of several marquee events planned to mark the 250th anniversary of the country, which will also include an IndyCar race around the National Mall later this summer and a "Great American State Fair" in July.
The weather could cause delays during the event on Sunday, with thunderstorms forecast in Washington DC.
It's going to be a hot and humid day on Sunday in the nation's capital, with mid-afternoon temperatures peaking at around 91F (33C), according to forecasts.
As the heat and humidity builds, scattered thunderstorms are expected to develop through Sunday afternoon and into the evening, with the risk of lightning, downpours and wind gusts of over 50mph (80km).
The summer humidity in Washington often attracts an unpleasant number of insects, and The Weather Channel is reporting that swarms of mosquitoes and gnats may find their way into the cage. It also said that a single lightning strike within eight miles of the fight could trigger a 30-minute freeze on the event.
A news conference for the event at the Lincoln Memorial on Friday was briefly delayed over "inclement weather" and fans were urged to seek shelter.
