One of the busiest days in motorsports has arrived.

The Formula One series kicks things off with the Monaco Grand Prix on Sunday, the jewel in the F1 calendar. After a difficult start to his title defense, Mercedes driver Lewis Hamilton has won the past two races and leads Ferrari’s Sebastian Vettel by 17 points.

Hamilton starts from third place on the grid behind Red Bull driver Daniel Ricciardo and Vettel. Ricciardo took the pole position.

The 102nd running of the Indianapolis 500 sees the career finale of Danica Patrick at the biggest race on the IndyCar calendar. She has stolen the spotlight for “The Great American Race” – but Helio Castroneves is chasing a record-tying fourth victory in the twilight of his IndyCar career.

NASCAR wraps things up Sunday night with one of its biggest races of the year, the Coca-Cola 600 at Charlotte Motor Speedway in North Carolina. Kyle Busch is on the pole. He has won a Cup points race at every track on the NASCAR circuit except Charlotte. Kevin Harvick has won the last three Cup races.

Thousands of fans have started pouring into Indianapolis Motor Speedway, where clothing is apparently optional with soaring temperatures this year, to see the 102nd running of the Indy 500.

The expected high is 93 degrees, which would eclipse the 1937 race as the hottest on record. Some 300,000 fans are expected at the speedway.

The temperatures are also causing concern for drivers. It’s hotter than it has been all month, and nobody is quite sure what that means for handling, passing and speed when the green flag drops.

Copyright 2018 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.