Missed it by a day: Why has the 52-year-old record for no rain in Phoenix lasted so long?

Yahoo

30-01-2025

Phoenix finally got a taste of rain Wednesday, but just barely. A scant 0.01 of an inch was recorded at Sky Harbor Airport, ending the city's 159-day dry streak, the second-longest on record.
While Phoenix is known for its arid weather, receiving 7.22 inches a year on average at Sky Harbor, this dry spell stood out from the rest.
"It doesn't rain here a lot, but we've got these two seasons that usually will cut these dry spells down," said Michael Crimmins, a climatologist at the University of Arizona. "Overall, this winter has been extremely dry, but Phoenix really stands out as having the longest dry stretch."
The streak ended just one day shy of tying the current record of 160 days without measurable rain in Phoenix, a record set in 1972. And it's still dry. With the .01 of an inch recorded Wednesday, Phoenix is still 2.68 inches below average since Oct. 1, the start of the water year.
Here's everything to know about Phoenix's dry spell, why the record is so hard to break and how other cities across the Southwest are faring during this unusually dry winter:
Topography and seasonal weather patterns play a big role in Phoenix's dry climate, setting the stage for long dry periods.
"Phoenix is standing on its own a little bit in Arizona. Phoenix is low desert and away from the mountains," Crimmins said. "It's easier to get precipitation in the high country."
Phoenix is surrounded by mountain ranges that can block moisture from reaching Phoenix. It's also far from large bodies of water that provide a consistent source of moisture to fuel precipitation.
Phoenix's low elevation prevents atmospheric lifting mechanisms that produce precipitation in higher elevations.
The rains can travel from the mountains, but it doesn't always happen. During the monsoon, the sun heats the mountains first and spurs conduction for storms. But as the systems descend, dry air at lower elevations and higher temperatures can cause a storm to die out before it hits the valley.
Low humidity and high temperatures also play a role, with extreme heat and dry air causing rapid evaporation in the Phoenix area.
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But why is the dry streak record so resilient? How has it stood for more than 52 years?
Although rain is less common in Phoenix than in much of the country, it typically measures a few inches of rain every year during the "wet" seasons in the summer and winter.
"We've got the monsoon in the summer and the winter weather pattern that can bring some precipitation," Crimmins said. "So that's just the seasonal cycle here — you get some weather system on the edges that usually breaks up the dry spells."
But this year was different. The monsoon began early with some showers in June but largely died out by the end of the summer. The last day of measurable rainfall was Aug. 22, beginning the second-longest dry streak on record.
"The dry spell was a byproduct of the monsoon not being great. We were already in trouble when the monsoon started to dry up," Crimmins said.
Arizona can get some moisture from fall tropical storms to the south, but September and October remained extremely hot and dry in Phoenix.
By December, Crimmins said the winter weather patterns that can bring precipitation south remained over British Columbia, one of the early signs of La Niña conditions.
La Niña is a climatological event that typically brings drier and warmer conditions to the Southwest, stemming from colder-than-normal ocean temperatures in the eastern Pacific.
This dry spell was also unusual because of its timing. Dry spells in Phoenix tend to occur in the winter and spring until the monsoon begins.
"It's totally normal to have 90-day dry spells in the spring until the monsoon kicks off," Crimmins said. "Phoenix recorded zero precipitation from Sept. 1 to now, and that hasn't happened before in the records at Sky Harbor."
Even during historically dry years, there were always two or three days that would break up the dry spells, according to Crimmins, making lengthy, 140-day-plus dry streaks uncommon.
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Phoenix isn't the only city with an uncharacteristically dry few months.
Las Vegas' dry streak is even worse — Wednesday marked the city's 200th day without measurable rain. This is also the second-longest dry spell for Las Vegas, but the longest streak is still a ways off. The current record was set in 2020 with 240 days.
It's been a dry winter across Arizona. Flagstaff has had one of its driest cold seasons on record with just 5 inches of snow since Oct. 1, compared to a 47.8-inch average for that time frame.
Yuma is also experiencing an ongoing dry spell at 174 days without measurable rain, but that does not come close to its record: 380 days, more than a full year with no rain in 2002 and 2003.
While Phoenix's dry spell has ended, residents likely won't see much rain in the coming months.
"Every day we get closer to spring, the chances of our precipitation events start to drop off," Crimmins said. "This is not a drought buster by any means. It breaks up the dry spell record, but it's not doing a lot of work otherwise.
Hayleigh Evans writes about extreme weather and related topics for The Arizona Republic and azcentral.com. Email her with story tips at [e-mail].
This article originally appeared on Arizona Republic: Why does the rainless record remain unbroken in Phoenix?