[5] The heat wave affected Northern California, Idaho, Western Nevada, Oregon, and Washington in the United States, as well as British Columbia, and in its latter phase, Alberta, Manitoba, the Northwest Territories, Saskatchewan, and Yukon, all in Canada.

The record-high temperatures associated with the heat wave stretched from Oregon to northern Manitoba, and daily highs were set as far east as Labrador and as far southwest as Southern California.

Extreme heat also damaged road and rail infrastructure, forced closures of businesses, disrupted cultural events, and melted snowcaps, in some cases resulting in flooding.

[11] The heat wave also caused extensive damage to agriculture across the region, resulting in substantial loss of crop yield and the death of 651,000 farm animals.

[3] On June 23, the United States National Weather Service warned of an approaching heat wave in the Pacific Northwest,[17] whose origins could be traced to torrential rains in China.

[19] At the same time, the Southwestern United States was enduring an intense drought [20] which caused higher-than-average temperatures, leading to a similar heat wave earlier in June.

[27] After the heat dome hovered over British Columbia and the Northwestern United States for a few days, it began to move eastward, bringing relief to the Pacific coast but breaking records east of the Rocky Mountains, particularly in the northern parts of the Prairie provinces.

[31] By July 4–5, the remnants of the heat dome crossed Hudson Bay and, weakened somewhat by the cool waters, entered Quebec,[32] and after that, Labrador,[33] briefly triggering temperatures of around 30 °C (86 °F).

[9] Broader climate shifts may have also contributed to worsening the heat wave; data provided by Verisk shows that the Pacific Northwest is among the fastest-heating regions in the continental United States and southern Canada.

[87] The heat wave resulted in 128 all-time high temperature records set for individual weather stations across the state, including in Seattle.

[93] Other localities in the Treasure Valley to the east were expected to sustain triple-digit heat for a week (which is in and of itself unusual) and in general to tie or beat daily records.

[97] Records were also beaten in the Idaho Panhandle, with Coeur d'Alene registering 109 °F (43 °C), which surpassed the previous highest temperature for June and equaled the all-time high for the city.

[3] On July 13, 2021, Multnomah County, Oregon published an analysis which found that a majority of deaths occurred in households which had no air conditioning or had only fans.

[120] The rate of air-conditioned households was even lower in British Columbia despite marked increases over the years – BC Hydro estimated that only 34% of the province's residents used air conditioning.

[124] Trying to stay cool, residents in the Pacific Northwest and Alberta rushed to buy A/C units, which significantly increased their prices (some double the normal), created long installation and delivery backlogs, and ultimately made them unavailable in many stores.

[128] The Idaho State Capitol voluntarily turned off lights as a result [129] and in the Spokane area, rolling power outages were used to reduce load on the grid.

[144] Similarly, numerous grocers were forced to shut down aisles and halt the sale of perishable goods or use plastic sheets as impromptu thermal shields, as refrigeration units failed under the load.

[145] The businesses that decided to stay open often provided de facto sheltering from heat or converted parts of buildings to cooling centers.

[146] In a few cases, workers in California and Oregon protested the lack of air conditioning and staged local walkouts,[147] and agricultural trade unions had also noted increased calls to strike.

Among the surveyed, about two-fifths reported not having had shade, just under a third not having received heat illness prevention training and a quarter of respondents had no access to cool water.

[153] Among other disruptions, a public swimming pool in Seattle's Rainier Beach neighborhood was closed due to dangerously high deck temperatures,[154] so was a senior's center in Rathdrum, Idaho[155] and a golf course on Vancouver Island.

[5] In the Prairie provinces, an infestation of grasshoppers is threatening cash crops[165] and farmers were reported to be struggling with feeding cattle as hay and forage was found to be in short supply.

[168] Further east, St. Laurent and Armstrong, Manitoba declared a "state of agricultural disaster" as the heat wave worsened the drought in the region, whose water reserves were already depleted.

This led to road closures, such as the U.S. Route 97 and the North Cascades Highway,[172] suspension of airport operations in Redmond, Oregon, and evacuation of settlements adjacent to the fires.

[175] Pyrocumulonimbus clouds formed due to such extensive burning, producing several hundred thousand lightning strikes in one day and further complicating efforts to contain fires.

[183] The Canadian army officials set up a coordination center in Edmonton in order to assist wildfire actions in British Columbia, which would be directed until July 19.

In April 2021, the North American wildfire season was predicted to be severe due to record drought conditions and high spring temperatures in the West.

[198] On Mount Rainier, the heat wave caused the mass of the snow cap to shrink by 30%, and Washington's glaciers in general have come through what glaciologists say to be the strongest melting episode in 100 years.

On the Pacific shore, temperatures in the intertidal zone reached up to 122 °F (50 °C) and more than a billion seashore animals, like clams, barnacles and oysters, died as a result of heat wave, impacting water quality.

[206] In Seattle, nearly a hundred juvenile terns, whose nests were on top of an industrial building, died when they plunged to the pavement below, presumably trying to escape the heat - those that survived were treated for burns.