“July 24, 2018 was one of the hottest days in California history, as a searing heat wave of rare intensity, even for the Desert Southwest, sent temperatures soaring to near-record levels. Death Valley hit 127°F, just 2° short of tying the all-time world record for hottest reliably recorded temperature; Palm Springs hit 122°F, just 1° short of tying its all-time record; and Imperial, California topped out at 121°F, their hottest day since 124°F was measured on July 28, 1995.
Figure 1. Hourly weather conditions observed in Imperial, California on July 24, 2018, courtesy of NOAA. Rain was observed for four consecutive hours beginning at 3:53 pm PDT, with a temperature of 119°F (48.3°C) occurring during the first two hours of the event. A big thank-you goes to weather records expert Jérôme Reynaud of Géoclimat for bringing this event to my attention.
The temperature might have gone higher on July 24 in Imperial, but clouds streaming in from the Gulf of California brought mostly cloudy skies by mid-afternoon, and rain showers began falling at 3:53 pm PDT. At the time the rain began, the temperature was an astonishingly high 119°F (48.3°C)—a new world record for the hottest temperature ever measured while rain was falling. A series of rain showers continued to affect Imperial in the late afternoon and early evening, with the station recording light rain for four consecutive hours. Most of the rain evaporated since the humidity was only 11 – 15% during the rain event, and only a trace of precipitation was recorded in the rain gauge. Nevertheless, the July 24 rain at 119°F in Imperial sets a new record for the hottest rain in world history.”
July has been one for extreme heat around the world, but every locale pales in comparison to what’s going on at Death Valley in California. Already one of the hottest places on the Earth, the heat has gone into overdrive this July.
At around 7:00 p.m. PT on July 26, a towering vortex of smoke and flame spun into the California sky. The tornado-like column rose over 16,000 feet into the air. It was a violent night for the Carr Fire, which after preying on profoundly dry forests, breached the Sacramento River and headed into the City of Redding, home to over 90,000 people.
A Nation Divided: Arid/Humid Climate Boundary in U.S. Creeps Eastward
To travel westward across the U.S. is to experience a striking landscape metamorphosis. Stately hardwood trees give way to squat shrubs, verdant cornfields to brown wheat and lush grasslands to cacti and creosote bush. The air dries out and the land is often parched. This rather abrupt shift from the humid east to arid west occurs along a border that slices neatly through the Canadian province of Manitoba, then the Dakotas, Nebraska, Kansas, Oklahoma, Texas and into eastern Mexico. The divide is so stark airline passengers can see it—a patchwork quilt of green farms on one side, a vast expanse of brown and gold on the other.
And now this boundary is on the move, creeping east as global temperatures rise, according to new research published last month in Earth Interactions. Given the line’s historical role in shaping U.S. westward expansion, its shift could alter the agriculture that plays a crucial role in the economy of the Great Plains states.
The 100th meridian west (solid line) coincides with the climate divide between the relatively moist eastern U.S. and the more arid West. Climate change may already be pushing the divide eastward (dotted line). Credit: Richard Seager Lamont-Doherty