This July, temperatures in London and Hamburg in northern Germany teetered over an edge that seemed unthinkable in previous centuries: 104 degrees (40 Celsius).

In large areas of the western and central United States, where temperatures routinely exceed 105 (40.5 Celsius), that may not seem particularly hot. But London and Hamburg are northern, maritime climates, where average July high temperatures are in the mid-70s (23 to 25 Celsius), and they don’t have close counterparts in the Lower 48 states.

To translate these records to cities in America, The Washington Post and the nonprofit Climate Central calculated how much warmer the record was relative to extreme high temperatures in London for the month of July.

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London and Hamburg are located near the equivalent latitudes of Calgary and Edmonton in North America and are within 50 miles of the chilly North Sea. They are nothing like relatively arid, landlocked southern cities such as Phoenix, Las Vegas, Dallas and Oklahoma City, where temperatures reached 110 this week. Even Seattle, Green Bay, Wis., and Portland, Maine, have warmer July average highs — around 80 degrees.

In smashing their all-time records, temperatures in London and Hamburg soared about 32 degrees (18 Celsius) above average. Simon Lee, an atmospheric scientist at Columbia University, said it was “surreal” watching temperature records fall in Western Europe and Britain. The heat wave “didn’t just break them by little margin like we’ve seen in the past,” he said. “It bulldozed them.”

London was one of at least 34 locations in Britain to surpass the U.K.’s previous all-time highest temperature — 101.7 degrees or 38.7 Celsius. The country sweltered under the heat, as the British people and infrastructure are not accustomed to such extremes. Steel rails in London expanded and buckled, while roads in Cambridge softened and bended. People flocked to cool off in public swimming pools or air-conditioned public spaces, as fewer than 5 percent of homes have air conditioning according to government estimates.

[Europe is overheating. This climate-friendly AC could help.]

The heat is a preview of extreme temperatures to come in the warming climate. The U.K. Met Office found that the country is now 10 times more likely to experience 40 Celsius than in a world untouched by human-caused climate change, emphasizing the need for better climate adaptation in the country.

The heat wave swept over the Iberian Peninsula last week, and Madrid matched its highest temperature on record: 105 degrees (40.7 Celsius). The mercury rose even higher in northwestern Spain, surpassing 109 degrees (43 Celsius) to set all-time records in Ourense and Ribadavia.

The government advised people to stay indoors and reduce physical activity. In a country where only one-third of homes have air conditioning, some flocked to their air-conditioned workplaces and public spaces.

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Temperatures remained warm through the night, and Madrid also experienced its hottest night on record at 79.1 degrees (26.2 Celsius). Elevated nighttime temperatures prevent people from cooling down and can increase heat stress, which can lead to heat exhaustion, strokes and death. In the last week, nearly 900 people in Spain have died of heat-related illnesses.

Combined with dry conditions, the extreme heat has also sparked wildfires that have consumed tens of thousands of hectares.

Dublin set a new July record at 91.4 degrees (33 Celsius), the country’s highest temperature in the 21st century. Huge crowds cooled down at beaches, and at least one wildfire appeared about 15 miles south of the Irish capital. The heat wave was intense but short-lived, with showers returning to the region this week.

Adrián Blanco Ramos and Kasha Patel contributed to this report.

The Washington Post and Climate Central calculated how much warmer each city’s record temperature was relative to the 99th percentile July high temperature from 1970 to 2021. Temperature data from London’s Heathrow Airport were used from 1973 to 2021. Temperature data is from the Global Historical Climatology Network.