LOS ANGELES (Reuters) -United Parcel Service ( UPS ) will retrofit 5,000 of its boxy, brown trucks with air conditioning in delivery areas with the hottest weather, according to the company and the Teamsters Union that represents the delivery firm's drivers.

UPS committed to add 28,000 air-conditioned delivery trucks in its current national contract. The 5,000 retrofits will help expedite that and offer drivers some relief from scorching summer heat, the Teamsters said late on Monday.

The first 2,000 vehicles readied under the agreement will be retrofitted by June 1, 2026. Air conditioning will be added to all 5,000 delivery trucks by June 1, 2027, and dispatched to the Teamsters' hottest delivery areas in mostly Southern and Southwest states, the union said.

The agreement also designates that 100 package cars will be upgraded with air conditioning vented into the cargo compartment under a new pilot program to evaluate strategies for greater heat relief.

"We are eager to start testing A/C in the cargo compartment, inarguably the hottest part of the package cars," said Karla Schumann, secretary-treasurer of Teamsters Local 104 in Phoenix, and chair of the package car heat committee.