LAS VEGAS >> The death of a 4-year-old boy who police said was left unattended in a stifling hot pickup truck on a 100-degree day illustrates one danger of intense summer temperatures in Las Vegas.

Autopsies reveal another.

Heat kills, and Clark County Coroner John Fudenberg said Monday his office has compiled data showing spikes in deaths when temperatures soar in summer in Sin City.

Forty-four people have died as of Aug. 20 from causes listed as environmental exposure, heat stress or hyperthermia, Fudenberg said. That makes 2015 the fifth year since 2005 that more than 40 people have died from heat-related causes in and around Las Vegas.

The biggest spike in recent years came in 2013, when Las Vegas baked for 15 days in late June and early July with daytime high temperatures above 105.

Temperatures averaged almost 111 degrees, and a record high of 117 degrees was set on June 30, 2013, the National Weather Service said. The hot spell broke 11 days later.

The coroner said 28 people died of environmental heat stress or hyperthermia in 2014, when the region had just eight straight days in late June and early July with temperatures above 101.

This year, Las Vegas spent 12 days between June 24 and July 5 with daytime temperatures above 101 degrees. The average daytime high was 108.5.

Fudenberg tallied cases listing environmental heat stress or hyperthermia as primary or secondary causes of death. More than half involved people with other illnesses as well.

"Ultimately what we can learn is to look out for loved ones and neighbors and make sure they’re OK," the coroner said.

According to doctors and safety officials, people most at-risk for heat-related injuries include children, the elderly and people with diseases and compromised immune systems.

Las Vegas police on Monday were still investigating the Thursday death of 4-year-old Seth Franz, who was left asleep in a black extended-cab Ford F-150 pickup in the driveway of a home about 5 miles east of downtown. The results will be forwarded in coming days to the Clark County district attorney, Officer Laura Meltzer said.

The boy’s father, Alan Franz, told KSNV-TV News3 in Las Vegas that donations can be made in his child’s memory to Three Square Food Bank in Las Vegas. The Associated Press was turned away from the family home on Friday has been unable to reach the father and other family members by telephone.

A Nevada law passed in 2005 after a spate of deaths and injuries to children in hot cars made it a misdemeanor to leave a child under 7 unattended in a vehicle.

The head of the advocacy group and website KidsAndCars.org said the death was the first in Nevada, but 16th of its kind in the nation this year.

Studies show temperatures in a closed vehicle rise 20 degrees in the first 10 minutes and 30 degrees within 20 minutes, said Janette Fennell, founder and president of the nonprofit. After an hour, temperatures in a vehicle can be 50 degrees higher than outside.

City and county agencies and a coalition of groups including Catholic Charities, Salvation Army and the Shade Tree women’s shelter offer free access to air-conditioned public and charity buildings as "cooling stations" during hot spells in the Las Vegas area.

A January tally found about 7,500 people living on the streets in southern Nevada, or about the same number of as in recent years.