PHOENIX (AP) — In a desert city used to triple-digit temperatures, some hunker down inside and some head to the pool, while others still want to hit Phoenix’s many hiking trails. But with temperatures creeping above 115 degrees during a heat wave boiling parts of the Southwest, that decision can have deadly consequences.

The mercury made a quick ascent Sunday for a high of 118, breaking a record of 115 set nearly 50 years ago, according to the National Weather Service. It tied for the fifth-hottest day ever in Phoenix.

The weather service forecast similar temperatures in Phoenix before they drop to 113 Tuesday and stay below 115 the rest of the week.

A 28-year-old woman and two friends set out mountain biking around 6 a.m. in north Phoenix and carried water, but she became exhausted about three hours later and then could not breathe.

Firefighters rescued the unidentified woman, who was an avid hiker and a personal trainer, and she later died at a hospital, fire Capt. Larry Subervi said.

Her death comes a day after a 25-year-old Phoenix man died of heat exposure while hiking in neighboring Pinal County.

Phoenix didn’t reach 120 as forecasters said was possible, but Yuma, in the southwestern corner of the state, did.