PHOENIX >> A severe heat wave ushered in the first day of summer today in the broiling Southwest, where extreme temperatures were blamed for at least five deaths over the weekend. Here’s the latest (all times local):

6:45 p.m.

Arizona cities saw more record-setting high temperatures, including the hottest day on record in Prescott.

The National Weather Service says Monday’s mark of 105 degrees in Prescott was the highest recorded in the city’s history.

Weather records go back as far as 1898.

Phoenix hit 116 degrees Monday, topping the previous record for June 20 of 115, set in 1968.

It was 112 degrees in Tucson, two degrees hotter than the mark set in 2005 for that date.

Portions of Arizona and southeast California are getting scorched by a high pressure ridge lifting out of Mexico.

5:50 p.m.

Authorities say a man who died and another who is missing after going for a hike in Arizona were from Germany and were in the state for a conference at a resort.

The men were in a group of three who went hiking Sunday on a trail outside the Tucson resort. One of the men is recovering, while 57-year-old Stefan Guenster was found dead.

The third man, 33-year-old Marcus Turowski, was still missing Monday.

Authorities didn’t release their hometowns.

The Pima County Sheriff’s Department says it likely would end its search at sundown Monday and resume Tuesday.

Tucson hit a record high of 115 degrees Sunday as a heat wave took over parts of the Southwest.

———

5:05 p.m.

Las Vegas has sizzled to 115 degrees and topped a record high temperature of 113 for the date set just a year ago.

National Weather Service meteorologist Nathan Foster said Monday it’s possible Sin City could reach another record Tuesday, when the predicted high of 113 would eclipse the record 111 in 1954.

Summer arrived Monday amid an excessive heat warning through Wednesday in southern Nevada, northwest Arizona and much of Southern California.

Foster says Las Vegas temperatures will ease through the week to a predicted 107 on Saturday.

Clark County officials have opened several recreation centers and other public buildings as air-conditioned cooling stations for people to beat the heat.

———

4:30 p.m.

Authorities say another woman has died as a result of the heat wave in the Southwest.

The Pima County Sheriff’s Department said Monday a 54-year-old woman died on Sunday night in Tucson walking along a loop trail. It brought the death toll to five in Arizona, where temperatures have exceeded 114 degrees.

The Pima County Sheriff’s Department reported three heat deaths on Sunday.

In addition, a Phoenix man hiking in the Superstition Mountains died from exposure to extreme heat. Pinal County Sheriff’s officials say 25-year-old Anthony Quatela III and a male friend ran out of water.

A 28-year-old woman who was mountain biking with two friends also died after running out of water and struggling to breath. Fire officials say the personal trainer was taken to a hospital, where she later died.

———

2 p.m.

Southern California is in the grip of a severe heat wave that has sent temperatures surging.

Numerous places across Los Angeles and neighboring counties passed 100 degrees well before noon Monday. The National Weather Service says the thermometer hit 121 degrees in Palm Springs by 1 p.m.

Forecasters expect Monday to be the peak of the heat wave.

The state’s power grid operator has called on residents to conserve electricity to avoid outages.

———

9:40 a.m.

Southern California is in for another day of dangerously high temperatures resulting from high pressure over the Four Corners region of the Southwest.

Forecasters say Monday will be the peak of the heat wave, with highs in the lower deserts to be near 120 degrees.

The National Weather Service reported 17 daily heat records broken on Sunday, most of them for readings well over 100 degrees.

The aptly named desert town of Thermal about 25 miles southeast of Palm Springs topped the list with a high of 119 degrees.

The Woodland Hills area of Los Angeles was 109, tying the record set in 2008. Burbank was a record 109, breaking the old mark of 104.

The temperature reached 96 in downtown Los Angeles.

———

9:20 a.m.

Two deaths related to extreme heat are being reported by search and rescue crews in southern Arizona.

Pima County sheriff’s Deputy Ryan Inglett on Monday confirmed the deaths of hikers in two separate incidents the previous day.

A 18-year-old woman suffering from heat-related illness died northeast of Tucson. The sheriff’s department says she and a companion had run out of drinking water.

On Sunday afternoon, search crews responded to a report of dehydrated hikers and found one man dead on another trail in the same area. Another hiker from that party is missing.

This item has been corrected to show the victim’s age was 18, not 19. The original information was provided by the sheriff’s department.

———

8:40 a.m.

Extreme heat forced a Phoenix-bound flight to return to Houston.

United Airlines says the hot weather led the plane to return to Texas on Sunday evening and that passengers will be accommodated with an added flight Monday morning.

The National Weather Service says the mercury hit 118 on Sunday, breaking a record of 115 set nearly 50 years ago.

Forecasters expect the same excessively high temperatures Monday in portions of Arizona and southeast California.

———

7:55 a.m.

The National Weather Service is expecting another day of triple-digit temperatures in Phoenix and across much of the Southwest.

National Weather Service meteorologist Biana Hernandez said Monday that temperatures in Phoenix are expected to peak at between 115 and 120 degrees, with the highest regional temperatures anticipated in Southern California.

The agency issued excessive heat warnings for Tucson and Yuma as well as recreation spots such as the Grand Canyon and Lake Havasu.

On Sunday, the mercury ascended to 118, breaking a record of 115 set nearly 50 years ago. Portions of Arizona and southeast California are getting scorched by a high pressure ridge lifting out of Mexico. The heat played a role in the deaths of mountain biker in Phoenix and a hiker in Pinal County over the weekend.