|Date||June 28 – October 4, 2018|
The 2018 North American heat wave affected regions of Canada, where at least 70 deaths in Quebec were heat-related, of the United States, where eighteen states between Michigan and New Mexico issued heat advisories to a population of over sixty million people, and of Mexico, particularly the northwest and central regions.
From 1 to 6 July 2018, the air temperature consistently rose above 35 °C (95.0 °F) in parts of Quebec and Ontario. The humidex value for Ottawa on Canada Day between noon and 3 pm was 47, the highest ever recorded in the city. The heat wave also affected the Maritimes, with the humidex value reaching 35 in Halifax and 45 at Greenwood in the Annapolis Valley, on 5 July.
On 4 July, Montreal emergency services reported twelve hundred calls per day about the heat, up 30% from prior busiest days.
As of 10 July, seventy-four people, most of them already ill, had died heat-related deaths in Quebec. This province's death toll is reported as much higher than others' because of its looser rules for attributing death to heat. In Ontario, where only accidental deaths directly caused by heat are counted, the coroner's office is investigating three possible cases.
While the heat wave ended on 10 July in Central Canada, this was not so for the Maritimes. On the 23rd of July, the interaction between a far-northwest Azores-Bermuda High and a trough over Ontario led to the issuing of heat warnings for all three Maritime Provinces, with several locations reporting humidex values in excess of 36. In Halifax, the heat wave contributed to a record-breaking number of hot days in July, with the airport reporting daily high temperatures in excess of 25 degrees Celsius on twenty-two days that month, breaking the previous record of twenty-one days set in 2008, 2003, and 1924.
On 8 and 9 August, temperatures reached high levels in Metro Vancouver. The daily highs in Abbotsford were 35.6 °C (96.1 °F) and 34.1 °C (93.4 °F) respectively. Temperatures on the waterfront of Vancouver reached 31.0 °C (87.8 °F) and 30.8 °C (87.4 °F). The hottest temperature reached in the Lower Mainland was 36.5 °C (97.7 °F) in Cultus Lake. Cranbrook broke its record for August of 37.2 °C (99.0 °F), and the all-time record of 38.9 °C (102.0 °F), with temperatures reaching 40.5 °C (104.9 °F). Creston broke its August record of 38.0 °C (100.4 °F), reaching 38.7 °C (101.7 °F), but did not break the all-time record. The largest city to break an all-time record was Calgary, with temperatures reaching 36.5 °C (97.7 °F). The previous record for August was 35.6 °C (96.1 °F), while the all-time record was 36.1 °C (97.0 °F). Temperatures in Lethbridge reached 40.0 °C (104.0 °F), breaking the previous August record of 38.9 °C (102.0 °F), and tying its all-time record.
On 6 July, the temperature at UCLA was 111 °F (43.9 °C), breaking the all-time high temperature record of 109 °F (42.8 °C) set in 1939 but still 6 °F (3.3 °C) lower than the record 117 °F (47.2 °C) set in Woodland Hills, a Los Angeles neighborhood, at about 1 p.m. local time the same day, according to the weather service. Elsewhere in California, Santa Ana and Ramona hit respective record highs of 114 °F (45.6 °C) and 117 °F (47.2 °C). The combined conditions of heat and dryness fueled wildfires that caused one fatality and hundreds of evacuations.
On 7 July, approximately 34,000 customers of the Los Angeles Department of Water and Power (about 2.5% of its base) experienced power outages, some for up to 24 hours. The previous day, peak energy-demand set a new record for any July day in the city, at 6,256 megawatts.
California's state authorities and the California Independent System Operator both urged power conservation by people and business from 5 p.m. to 9 p.m. on July 24 and July 25, 2018. Flex Alerts were issued as the power grid began to overload. The Los Angeles County Department of Public Health also urged people to stay out of the sun on July 24. Thousands lost electricity in California due to sporadic temporary power cuts on July 24 as record temperatures hit the southwestern United States, including much of Arizona and parts of California and Utah.
The forest fires that started near the Sequoia and Yosemite National Parks on July 13 grew Jul 22, 2018. The fires were visible for several miles on the south side of the Mineral King Road and Slapjack Creek, a National Park officials said on July 22. The Atwell-Hockett Trail and the Tar Gap Trail are closed due to the fire, But the Sequoia and Kings Canyon National Parks remain open on July 22. A bulldozer on July 13 and 4 firefighters had died by July 22. More than 2,800 firefighters, a fleet of aircraft and bulldozers had contained only 7% of its perimeter by July 22. An air tanker dropped fire retardant drop on the Horse Creek Fire in Sequoia National Park.
Several fires hit Whiskeytown, California; whilst others expanded past the Sacramento River and into Redding, California on July 28. At least 500 homes, businesses and other structures have been destroyed and 5 died by 28 July.
About 12,000 firefighters battled to contain wildfires in "erratic" winds across northern California on July 29. 6 Californians and 5 others elsewhere had died by June 29. 
Phoenix, Arizona recorded 111 °F (44° Celsius) on July 6, 2018 which was 5 °F (3° Celsius) below the record on this date of 116 °F (47° Celsius) and 11 °F (6° Celsius) lower than the all time high of 122 °F (50° Celsius) set on June 26, 1990
By the end of May 2018, Mexico was already one week into the heat wave. The states of Baja California, Sonora, Nayarit, Jalisco, Oaxaca, Coahuila, Durango, Zacatecas, San Luis Potosi, Querétaro and Morelos registered temperatures between 40 °C (104.0 °F) to 45 °C (113.0 °F), while Sinaloa, Chihuahua, Michoacán and Hidalgo between 45 °C (113.0 °F) and 50 °C (122.0 °F). Chihuahua broke its 1978 mark and Sinaloa surpassed the high recorded there in 1961.
By early June 2018, the Mexican government had declared a state of emergency in more than three hundred municipalities. The extraordinary sales of cold beverages, ice creams, pops and other items popular during hot weather increased to such an extent that Canacope Puebla, a Mexico City business chamber, estimated the nation's GDP would increase by approximately 260 million pesos ($13 mln).