Visitors to Greece appear ill informed about heatwave risk
Eric Calibet, 59, a retired Los Angeles police officer
temperatures were slated to exceed 37C.
That's 98°F. That's not incredibly hot by California standards.
I doubt that a Californian visiting Greece is unfamiliar with high temperatures. In general, the US sees greater temperature extremes than Europe, and while Greece is hot as Europe goes, California is home to the hottest temperatures in the world.
https://en.wikipedia.org/wiki/List_of_extreme_temperatures_in_Greece
Greece holds the record for the highest maximum temperature recorded in Continental Europe, with 48.0 °C in Elefsina and Tatoi (both located in the Athens metropolitan area) Greece holds the record for the highest maximum temperature recorded in Continental Europe, with 48.0 °C in Elefsina and Tatoi (both located in the Athens metropolitan area)
https://en.wikipedia.org/wiki/U.S._state_and_territory_temperature_extremes
California: 134 °F (56.7 °C)
Los Angeles itself is coastal, so more moderate, but it still gets rather hotter than 98°F.
https://www.extremeweatherwatch.com/cities/los-angeles
The highest temperature ever recorded in Los Angeles, California was 110 °F which occurred on September 26, 1963.
That'd be 43°C.