Runners looking forward to competing in Wednesday's Red, White and Boom half marathon in the Twin Cities will be disappointed to find out that it's been cancelled. 

TwinCities in Motion, the event's organizer, called the half marathon off due to expected unhealthy heat levels on Wednesday. 

"Due to expected heat and extreme humidity on race day, the half marathon distance at Wednesday morning’s Red, White & Boom! has been cancelled," TwinCities in Motion said in a statement. 

Registrants for the half marathon have the option to run a shorter race, either the 5K or a 6.75-mile race. 

The 5K was already scheduled but they added the 6.75-mile race as a substitute for the half marathon. The 6.75 miles will be two laps of the 5K course. 

The half marathon was scheduled to begin at 6:30 a.m., but organizers consulted with medical professionals and "deemed the conditions too extreme for a safe half marathon race." 

Temperatures on Wednesday are expected to climb into the low 90s with heat index values possibly exceeding 100 degrees, although it won't be quite that hot early in the morning. 

The 5K and the 6.75-mile race both start at 6:50 a.m. 

Half marathon registrants should've received an email on Monday with a half-price discount for a future TwinCities in Motion half marathon.