With a major heat wave prompting safety warnings across the Eastern two thirds of the country, organizers canceled Sunday’s scheduled 19th New York City Triathlon.

With temperatures expected to hit 99 degrees and high humidity raising the heat index to reach 105 to 110 degrees, organizers said that the Manhattan event would be beyond safe racing conditions.

“Safety is key for every athlete in this event and the decision although a tough one, is the right one at this time!” announced race director Bill Burke. “My heart goes out to every athlete that has trained and traveled to the Big Apple for the 19th edition of this great American Endurance Event.”

Nearly 4,000 competitors will receive full refunds of their entry fees within two to three weeks, organizers said. “After exhausting all options to mitigate athlete, volunteer, spectator and staff exposure alike, we are unable to provide either a safe event experience or an alternate race weekend," said Burke.

The race drew registrants from 33 countries and 45 US states and would have had participants swimming 1,500 meters in the Hudson River before cycling 40 kilometers and running 10 kilometers in Manhattan’s Central Park.

The heat wave is canceling other sporting events around the nation, including horse races in New York state and Maryland.

Burke said this was just the 5th cancellation in his 41 years of endurance event production. “I've been a part of just 5 completely canceled events,” said Burke. Three for weather related issues and two from the terrorist attacks of 9/11 on this country!”