The water temperature should be in the mid 70s.
Wetsuits can be worn in water temperatures up to 78 degrees without penalty. If a wetsuit is worn in water temperatures of 78.1 to 84 degrees, the participant becomes ineligible for age group awards, but can still race. The water temperature will be announced on social media the day before and the morning of the race.
For more information go to: https://www.teamusa.org/usa-triathlon/about/multisport/competitive-rules#article%20IV