US Open 2018: Top guns Federer, Djokovic and Wozniacki through

Five men's players were forced to retire on Day 2 as conditions in New York were described as dangerous.

As per reports, temperatures rose close to 38ºC and humidity skied past 50% mark.

Extreme heat policy for men's matches was implemented for the first time by the tournament organizers owing to the conditions.

It was a sorry sight to see environmental issues impacting players.

World number two Federer surged into the second round after a routine 6-2, 6-2, 6-4 win over Japan's Yoshihito Nishioka.

The 37-year-old hit 56 winners and will face France's Benoit Paire in round 2.

2018 Wimbledon winner Djokovic struggled in the humidity but still defeated Marton Fucsovics 6-3, 3-6, 6-4, 6-0.

He was unsteady on his feet and asked for a sick bucket.

4th seed Alexander Zverev eased past Canada's Peter Polansky to progress to the second round after a 6-2, 6-1, 6-2 win.

7th seed Marin Cilic beat Romanian Marius Copil and was joined by Nick Kyrgios.

Veteran Frenchman Julien Benneteau, David Goffin, Richard Gasquet and Gael Monfils were the other big names that made it to the next round.

World number two Caroline Wozniacki saw off Sam Stosur under extreme heat conditions in a 6-3, 6-2 duel.

The Dane will be up against Lesia Tsurenko next.

Joining Wozniacki was fourth seed Angelique Kerber.

The 2018 Wimbledon champion beat Margarita Gasparyan 7-6, 6-3.

Petra Kvitova progressed, as well, after beating Yanina Wickmayer 6-1, 6-4.

Last year's semi-finalist CoCo Vandeweghe was beaten by Belgian Kirsten Flipkens.

Latvian 10th seed and 2017 French Open winner Jelena Ostapenko overcame Andrea Petkovic 6-4, 4-6, 7-5.

Kiki Bertens won 6-0, 7-5 against Czech Kristyna Pliskova.

Japan's Naomi Osaka too prevailed in 6-3, 6-2 win over German Laura Siegemund.

Maria Sharapova beat Patty Schnyder 6-2, 7-6 in her opening round match.