Jonathan Jurejko
BBC Sport at Flushing Meadows

The Americans know how to ramp up the excitement at a sporting event.

Darkness descends, strobe light flash, BPMs rev. Feels like a David Guetta gig rather than a tennis match.

Here we go. The lights go out without just spot lights flashing around the stands like a music gig.

The players are introduced like boxers to the ring.

Serena gets a huge ovation.

Jeff Tarango
Former professional tennis player on BBC Radio 5 live sports extra

The match is on Serena's racquet but there is all of the hype. Does that distract her in these matches?

It's almost time. The players are in the corridor leading to the court and are about to have their chat with American TV which has become a fixture of this tournament.

Jonathan Jurejko
BBC Sport at Flushing Meadows

Image source, BBC Sport

For the first time over the past fortnight, the heavens have opened over Flushing Meadows.

Rain is splattering down outside, with the outside courts and plaza in front of Ashe - usually buzzing as people file into the stadium for the night session - deserted.

A flash catches my eye... was it lightning? A roll of thunder confirms it was.

Storms were forecast from earlier in the day, meaning the United States Tennis Association decided not to take any chances and announced they would be keeping the roof on Ashe closed tonight.

Indoor tennis it is.

Image source, Getty Images

The second semi-final tonight sees last year's runner-up, American Madison Keys take on 20-year-old Naomi Osaka.

Osaka is appearing in her first Slam semi-final and is fulfilling her billing as one of the brightest young players in the game.

She is the first Japanese woman to reach a Grand Slam semi-final since Kimiko Date at Wimbledon in 1996.

That one should be a cracker.

Punctuality has not been a strong point at this tournament. We're still waiting for the players.

As ever this is a whole lot more fun if you get involved, especially when I'm typing away in the early hours.

I want to know who you want to win and why, who you think will win and your thoughts on the tournament so far.

Tweet us at #bbctennis or text 81111 (charged at your standard message rate).

These two have certainly had differing careers with Serena Williams one Slam away from Margaret Court's record of 24 and Anastasija Sevastova appearing in her first semi-final.

One similarity though is both had a period away from the game.

Williams missed 14 months before and after giving birth while Sevastova retired from the sport for two years before returning in 2015.

Since then she has reached two US Open quarter-finals and this semi. Good decision to come back...

David Law
BBC Radio 5 live sports extra commentator at Flushing Meadows

The roof will be on for Serena Williams vs. Anastasija Sevastova and Madison Keys vs. Naomi Osaka tonight. Thunderstorms expected. We rejoice on both counts given the awful humidity here. But it could make for a weird sound again.

Image source, Getty Images

But Serena isn't getting ahead of herself.

She says there is still a "really long way to go" for her to win a record-equalling 24th Grand Slam singles title at the US Open.

The American has lost her last two US Open semi-finals and also was beaten by Angelique Kerber in the Wimbledon final earlier this year.

"I'd been a couple of steps away at the last Grand Slam, so I'm definitely not ahead of myself," Williams said.

"I still know that no matter whether I'm in the semi-finals or the finals, I have a really long way to go to win."

Image source, Getty Images

After a year away Serena Williams is back in the semi-finals of her home Grand Slam.

She missed last year's tournament due to the birth of her daughter Olympia but this year is back and is the only Grand Slam champion left in the draw.

The 36-year-old is the overwhelming favourite.

Today she is up against a player appearing in her first Grand Slam semi-final - Latvia's Anastasija Sevastova, the world number 18.

Image source, Getty Images

Hello there! It's semi-final time.

We're set for another late one from the city that never sleeps.

Over the next few hours the women's finalists of 2018 will be decided.

First up is someone who knows just a little about nights like this...

128 players started. Now just four remain.

It's Ladies' Night under the lights in New York...

Image source, Getty Images