Opening Day at Del Mar in 2015
Horses move from the Paddock area to the racetrack prior to a race. Chris Stone photo

Horse racing officials defended their decision to hold races at Del Mar Thoroughbred Club over the weekend despite the extreme heat wave gripping Southern California.

A small number of animal rights activists protested at the track Saturday, arguing that forcing horses to run in extreme heat was cruel and calling for the track to cancel races scheduled over the Labor Day weekend due to the ongoing heat wave that has gripped the entire state.

But officials with the track and the state regulatory board said precautions were in place to protect the animals.

“Stewards and veterinary personal have been constantly monitoring the weather at Del Mar and calculating the heat index (temperature plus humidity, minus wind velocity),” said Mike Marten, California Horse Racing Board spokesman.

“At no time has the heat index risen to the point of cancellation. Still, horsemen and all concerned have been taking steps to protect the horses, largely by making sure they always have plenty of water and by hosing them down frequently. Veterinary personnel report there have been no serious incidents caused by the weather/racing,” Marten added.

Del Mar spokesman Mac McBride told City News Service that there were “no problems with heat” at the track this weekend, adding that the “ocean breezes works to our advantage.”

The CHRB uses something called the Heat Stress Index to determine when it’s too hot to hold races. The number is calculated by adding the current temperature and relative humidity.

If that number exceeds 175, no racing or training is permitted.

If it exceeds 160, any determination to proceed with racing or training requires the approval of the stewards based upon a recommendation from the official or association veterinarian.

If exceeds 150, horses’ cooling mechanisms are reduced and supplemental cooling must be provided, according to the CHRB.

According to the National Weather Service, the temperature reached 89 degrees in Del Mar on Saturday with relative humidity topping out at 82. The high was 86 Sunday, with relative humidity reaching the low 70s.