Everything you need to know about Arizona’s weather

PHOENIX (3TV/CBS 5) - From its lowest elevation, about 100 feet above sea level along the Colorado River, to the top of Mount Humphries near Flagstaff at 12,611 feet, Arizona has weather for just about everyone.

Everyone knows it’s hot in Arizona. And it is, in the deserts. But Arizona is more than just desert. In fact, of the more than 30 climate classifications, Arizona has 11 of them including tundra. Yes, there’s a small area of “tundra” in Arizona. One type of climate you don’t find in Arizona is tropical, but there’s a wide range of climates and temperatures.


Arizona hikers love sunrise hikes.
Arizona hikers love sunrise hikes.(3TV/CBS 5)

Let’s start with the easy stuff, the sunshine. It’s very sunny around the entire state most of the year. In Phoenix, we see about 300 sunny days. Yuma, in southwest Arizona, is the sunniest city in the state with more than 320 sunny days. Even in Flagstaff, in the mountains, we see about 260 days with sunshine.

Protection against the sun is the must, even during the winter and especially at the higher elevations of the state where there’s less atmosphere to protect you from harmful UV rays.

Tom's Thumb in the McDowell Mountain Preserve.  If you're a hiker, this one is a must.
Tom's Thumb in the McDowell Mountain Preserve. If you're a hiker, this one is a must.(3TV/CBS 5)

OK, it’s time to talk about the desert heat. It can be brutal. The hottest temperature recorded in Arizona was 128 at Lake Havasu on June 29, 1994. There’s still but a bit of controversy whether the actual date of the record was the 29th or the day before, but everyone agrees about the temperature.

In Phoenix, the record high temperature is 122 degrees. It occurred on June 26, 1990. Five years later we made a run at the record and got to 121 degrees on July 28, 1995. But we’ve been very close to breaking the record since then.

But it’s still hot and getting hotter. Ten of the 23 hottest days on record in Phoenix have occurred since 2000. And it’s the lows that are really on the move. In the 1980s, the average summer low in July was 81 degrees. Now it’s 83. In July 2018, the average low was nearly 86 degrees.

We just don’t cool off like we used to when the city was smaller. The warmest low ever in Phoenix is 96 degrees. And we’re waiting, because it’s almost sure to come, for the day when we have a low temperature of 100. That will be a sad day in Phoenix weather history.

The average high in July tops out at 107 degrees but the hottest day of 2018 was 116 degrees.


The flip side of the 100-degree weather, which usually starts popping up in April, is the beautiful fall, winter and spring.

The triple-digit highs are over with by Halloween, and while much of the East is getting ready for the deep freeze, mild temperatures become the norm around metro Phoenix. In December, average highs are around 66 degrees with lows around 45.

If you don’t want to deal with excessive heat, check out one of our mountains locations, say, Prescott. It’s at a mile in elevation and, as you might expect, it’s not as warm. The record high is “only” 105 degrees but average highs in July run around 90. And you get much cooler nights in the high country. Prescott’s average low in July is in the 60s.


A storm hits Phoenix Sky Harbor on Monday, July 30. (Source: James Stamsek)
A storm hits Phoenix Sky Harbor on Monday, July 30. (Source: James Stamsek)(James Stamsek)

Generally, the farther south and east you go in Arizona, the more precipitation you can expect. While Phoenix gets, on average, about 8 inches of rain every year, Tucson gets about 12 inches and Bisbee, in southeast Arizona, gets about 19 inches of rain.

By contrast, areas along the Colorado River in western Arizona generally get the least rain. Parker gets about 6 inches of rain annually; Lake Havasu gets 4 inches and Yuma only about 3 inches. In fact, in 2007, Yuma recorded only 0.15 of an inch of rain all year! That’s dry.


Snow in Flagstaff. (Source: Elise Wilson)
Snow in Flagstaff. (Source: Elise Wilson)(Elise Wilson)

In the mountains of Arizona, snow is very common above 6,500 feet in elevation during the late fall and winter. And yes, it has snowed in Phoenix. The record snowfall is 1 inch. That occurred twice in the 1930s. And the last time Phoenix had measurable snow was Dec. 21, 1990. It only measured about half an inch.

But the high country is a much different story. The mountains receive snow every year and some places get a lot of it. Flagstaff gets more than 100 inches of snow each year. The south rim of the Grand Canyon gets more than 115 inches!

In the White Mountains, the snowfall is also impressive. Some areas, including the small town of Greer, get nearly 20 feet of snow every season.

The snow is very important to the entire state for two reasons: recreation and water supply.

The recreation part is fun. There are two major ski areas in the state. They are Arizona Snowbowl near Flagstaff and Sunrise Ski Resort in eastern Arizona’s White Mountains. There are also numerous other winter recreation activities from cross-country skiing to sledding and snowmobiling.

The water supply part is important to every resident of the state. The winter snowpack, when melted, fills the reservoirs that contain much of the water supply in Arizona. Other main sources of water are groundwater and water from the Colorado River. But the winter snowpack is very critical. A few years of dry winters can lead to water cutbacks.


Monsoon dust storm moving into the Phoenix metro area

Source: 3TV/CBS 5 file
Monsoon dust storm moving into the Phoenix metro area Source: 3TV/CBS 5 file(3TV/CBS 5)

You may have heard about the Arizona monsoon. It’s part of the North American monsoon which includes Arizona, New Mexico, Colorado, Utah, west Texas and northern Mexico. There are at least eight different monsoons in the world, including the most famous monsoon that impacts India. Although the Arizona monsoon doesn’t bring nearly as much rain as the Indian monsoon, it’s very important to the region.

Microbursts are common during the monsoon.  

Source: 3TV/CBS 5 file
Microbursts are common during the monsoon. Source: 3TV/CBS 5 file(3TV/CBS 5)

The word “monsoon” comes from the word mausin, Arabic for “season” or “wind shift.” It is now used to refer to a seasonal wind shift and the precipitation produced as a result. In Arizona, the monsoon is caused by very warm air creating surface low-pressure zones that in turn draw moist air from the oceans. Arizona winds usually come from the west, but shift to a southerly wind in the summer, bringing moisture from the Gulf of California and the Gulf of Mexico.

The wind shift and increase in moisture combine with the surface low pressure from the desert heat to produce storms in a cycle of “bursts” (heavy thunderstorm rainfall) and “breaks” (reduced rainfall). Before the rain, the wind shift can trigger dust storms which can tower 5,000 feet into the sky and stretch for 100 miles or more.

In Arizona, the rainfall rule of thumb also holds for the monsoon. The farther south and east you go, generally, the more rain you will see. While Phoenix gets less than 3 inches of monsoon rain annually, Tucson gets 6 inches and Flagstaff gets 8 inches of summer rain. The nature of monsoon rain, generally coming very quickly, leaves much of Arizona prone to flash flooding.

The monsoon “season,” as it’s called, lasts from June 15 to the end of September. For the Valley, however, summer thunderstorms usually don’t arrive until around July 4 and last until about Labor Day.

A Cave Creek wash is flooded with water following a monsoon on July 16. (Source: 3TV/CBS 5)
A Cave Creek wash is flooded with water following a monsoon on July 16. (Source: 3TV/CBS 5)(3TV/CBS 5)