No major city in the United States was hotter than Seattle on Monday, according to temperature readings.

Miami got up to 85 degrees, Houston hit 79 and Las Vegas checked in at 78, but only Seattle and Phoenix reached 87 degrees.

For Seattle, it was the highest temperature recorded on May 6 since 1948 when the National Weather Service began measuring Seattle’s official temperatures at Seattle-Tacoma International Airport. It was also the earliest in the year it has ever been that warm, and it was the hottest day since Sept. 7.

“Yeah, it’s pretty hot outside,” deadpanned Josh Smith, a Weather Service meteorologist, after the 4:53 p.m. reading at Sea-Tac.

Or, as Seattle comedian Mona Concepcion tweeted:

“Stop being so hot, Seattle! I haven’t lost enough winter fat to wear shorts yet!”

The heat, which shattered the May 6, 1957, record of 79 degrees, capped an unseasonably warm first week of May.

Smith said the average high for the month, so far, has been 75.5 degrees. In May 1992, the average high for the entire month was 71 degrees, a May record.

Sunday’s high of 84 degrees came just short of the record of 86 for that date. And the two-day heat wave represented the first back-to-back May days above 80 degrees since 2008.

But Tuesday is not expected to challenge the May 7, 1987, record of 81 degrees. The forecast calls for a high of 72. Then temperatures should remain in the low 70s with partly cloudy skies for the rest of the week, Smith said.

The reason for the brief heat wave? Smith pointed to a “thermal trough,” of low pressure that arrived from the south and is temporarily causing wind to move from the east toward the coast.

Whatever the reason, Western Washington residents happily took advantage of the heat by flocking to parks and beaches.

Most of them, at least.

Others complained, like Concepcion and a Twitter user who calls herself @yukilicious247.

“i feel like a melting Popsicle,” she tweeted. “it’s way too hot for Seattle.”

Brian M. Rosenthal: 206-464-3195 or brosenthal@seattletimes.com. On Twitter @brianmrosenthal