Updated 7/21/20. For all you who may be contemplating a visit or move to the Old Pueblo, did you ever wonder what the weather patterns are like in Tucson? Or did you recently move to Tucson and want to know what to expect?
Perhaps you heard that it gets hot here. But how HOT is HOT? Moreover, how does Tucson weather differ from that of Phoenix to the north or from Tombstone and Bisbee weather to the southeast? A hundred miles in any direction from Downtown Tucson can make a big difference in the weather.
Ms. Karen here. A former Navy brat, I have now lived in Tucson longer than I have lived in any other one place. I never before stayed anywhere long enough to recognize the patterns of weather and rhythms of nature, or to plant a garden.
That said, I have been here long enough now to have witnessed that Southern Arizona has not 4, but rather 5 seasons: Winter, Spring, Dry Summer, Wet Summer, and Fall. Tucson averages about 12 inches of rain a year, making the Sonoran Desert the wettest, lushest desert in the world.
On average half occurs in winter and half in summer. As a “Rule of Thumb”, our wet summers start July 4th and end on Labor Day. However, that generality can vary by two or even three weeks either way.
Summer Rains
Tucson’s summer and winter rains are quite different. Summer heat brings on the monsoon season with thunderous rain storms and blustery or even gale-force winds arriving from the southeast, blown in from Baja Mexico and the Gulf of California.
We live in the foothills of the Tucson Mountains. From our kitchen window and upper viewing deck, we look out east over the city. In monsoon season, we watch the thunderheads build up in the afternoons over the Tucson basin from the east. Often they drop their moisture like a giant bucket of water on only a portion of the population, leaving the rest of the city bone dry.
Sometimes only the east side gets wet. Other times it’s our turn. A summer storm can easily drop 2 inches of rain on Tucson and in the process lower the temperature from 106 to 86 in 20 minutes.
Such a deluge floods our city streets, particularly in mid-town and downtown underpasses. Traffic in these low areas come to a halt. However, once the rain subsides, the water level in the streets declines rapidly. An hour after the rain tapers off, the streets are mostly back to normal.
Stupid Motorist Law
We do have a Stupid Motorist Law. Signs are everywhere: “Do Not Enter When Flooded”. Take heed! When a dip in the road is flooded it is very difficult to estimate how deep the water is. Eighteen inches of water will stop most sedans. And while the water may seem slow-moving it is powerful. It does not take much for these temporary rivers to push a car off the road and down stream. If this happens to you, you can call 911 and emergency personnel will try to rescue you. But they will also send you a bill.
Fortunately, we have good drainage channels. Many were once perennial streams, such as Pantano Wash to the east, Rillito River east to west, and the Santa Cruz River, north-south on the westside. La Canada Wash has been a problem for years.
Flash Floods
Some of these storms bring killer flash floods.
This last is not hyperbole. Way too often, folks enjoying a picnic or hike in our canyon streams drown and are washed away by flash floods. Survivors invariably tell the same story.
“We were enjoying beautiful weather wading in the cool steam. We had no idea we were in any danger … until a wall of water 20 feet above our heads crashed down on us.”
In 2017, one family lost 10 members ranging from grandpa to infant in a matter of seconds. A horrible tragedy, but not all that uncommon.
Boulders the size of houses come crashing down. Roads and bridges are quickly washed out. Both Sabino and Tanque Verde Canyons are infamous for such death and destruction.
How does this happen? Watch as the thunderclouds build up over the mountains, then in less than an hour, dump 4-6 inches of rain on higher elevations miles from the peaceful canyons below. All that water has to go somewhere. The once dry cliffs quickly become majestic waterfalls. The canyon streams fill quickly. Be wary, be careful.
Winter Rains
Winter usually brings a more soaking, Oregon-type rain, the all day kind, and then sun, glorious sun. Take in the pungent smell of creosote. These rains determine the wildflower season we will have in the spring. Some years bountiful Mexican poppies cover the hills, a magnificent sight.
Picacho Peak Wild Flowers
One of the best places in Southern Arizona to enjoy and photograph spring wildflowers is Picacho Peak State Park about 50 miles north of Tucson. Another great wildflower area is around Ajo.
Arizona is desert and in the desert there are extremes of temperature and biodiversity.
Day and night temperatures typically vary by 30 degrees. Traveling up Mt. Lemmon you will pass 4 biodiverse ecosystems. The temperature on the desert floor can be 107, while the top of Mt. Lemmon may be in the low 70’s.  In the high desert, like Bisbee,  you will most likely see snow in the winter. Cochise County receives more rain in the summer than Pima County. I suppose the altitude and rain in Cochise County is why grapes for wine making do so well. The winemakers also claim the soil is better. You decide.
Following is a brief description of what you may expect from month to month.
January
Temperatures can range from the teens to the 70’s, but mostly it is 40’s at night and 60’s during the day. My personal opinion is that January is the dead of winter here. As soon as the sun goes down the temperature drops. Mesquite trees finally lose their leaves. The winter storms blow what remains of leaves into the pools. Color is provided by a few Baja fairy dusters and Barrel Cactus fruit. Prune your roses and plant bareroot roses. Be mindful that roses require a lot of water and water is only going to get more expensive. We can get a hard freeze for a week of nights or none at all, like this year. Bisbee will get frequent snow showers. It is higher in elevation and cooler.
February
It is warming up although it could still freeze. Uncover your frost sensitive plants but be prepared to cover them up for a night, maybe two. Penstemon are the first to bloom. They are the daffodils of the Southwest, the harbingers of spring. Â After a rain the Ocotillo will leaf out and bloom.
March
March weather is close to perfect. The nights may still be a little cool, 50’s, but the days are sublime. Winter storms are gone and trees are leafing out again. Wildflowers abound in the parks and hills. Picacho Peak (Peak Peak) can spawn a spectacular showcase of color.
Lady Banksia roses are going to begin budding. depending on the kind of winter we have had they may be in full bloom by mid to late March. In Tombstone is cooler, so you will see the Lady Banks Rose that takes up a full city block bloom later. The Rose Festival honoring this old rose is always sometime in April. Planting season has begun for trees, fruits, veggies, and flowering plants.
April
You may have some warm days in April though usually not in the 100’s yet. Nights are in the 60’s. Perfect. The weather is still good. It can be windy, very windy. It spreads the seeds for the next crop!. It is also allergy month. Flowers everywhere!.
The snow birds have left to enjoy spring in the northern states. Oh, yeah. Snakes come out this month. Watch your step.
The Arizona Sonora Desert Museum ends their Free Flight program this month. It gets too hot to fly the birds.You can see the birds fly and hunt from October – April.
Did I mention that it can be quite windy this month?
I love to walk at sunrise and listen to the birds wake up. You can hear Gambel’s Quail, Cactus Wren and the occasional Pyrrhuloxia (Southern Cardinal) calling in the distance. Except for the wind, it is my favorite month.
May
Get ready for Summer. Â Overall temperatures this month can vary widely. Put your shade screens on your windows. Shade your roses, tomatoes and veggies. Most likely we will have our first 3 digit days, although a hundred degree day may have arrived in April by surprise. As the weather heats up the cactus begin to bloom. Saguaro may bloom this month or early June. Cholla blooms in all colors except blue are common.
June
Ah, June. The hottest month, dry with no rain in sight. A likely occurrence near the end of June or early July is Bloom Night. Bloom Night is a special once a year occasion when the native Night Blooming Cereus, opens and delivers its pungent honey scent into the air. Bees will get out early this day to be the first to arrive and partake of the luscious flower’s pollen. Heavenly. The flower only stay open until the sun hits them, so go out early. Tohono Chul Park is famous for its Bloom Watch and Bloom Night. On that night they will stay open late, so that visitors might see this wonderful event. It is worth putting up with the heat just to witness this.
You can try an escape to Bisbee this month, it will be cooler but perhaps not cool enough. Mt. Lemmon, Mt. Graham or Carr Canyon are your great escapes. And of course, further north are the White Mountains and Flagstaff.
July
One of the unofficial beginnings of Monsoon season is the 4th of July. El Dia de San Juan (St. John the Baptist) is June 24th. Realistically, it usually arrives much later. Moisture begins to build and the humidity rises. As the humidity rises, our swamp coolers are less effective and we become more and more uncomfortable. The first rain of the monsoon will undoubtedly not be far behind. Then, temperatures can drop 30 degrees in a few minutes. Glorious. Barrel Cactus tend to bloom this month.
August
By August, monsoon is in full swing. It may rain every day or once a week. Thunderstorms are a common, sometimes daily in parts of the Southwest. Clouds build during the day, come up from the gulf and result in a sound and light show in the late afternoon. Rain can be heavy, accompanied by strong winds.
Do NOT drive through a running stream that may occur in the middle of the road. You will be swept away and will pay the price. Pull your car over, or turn around. It never lasts long but can be spectacular. Be mindful where you hike. Check the weather. It may not be raining where you are but on the mountains above you it could be pouring down and runoff builds quickly. Be careful and know your escape.
September
This is the month we wait longingly for it to cool down at last. Usually this does not happen until after mid month. Relax, don’t be in a hurry to do your fall planting or prune your roses if you dare to have them. Towards the end of the month we should get some relief.
October
Hooray for October! Yay for Fall! Nights are cooling down. We can open the windows again and enjoy the night air. You can plant again. Aloe can bloom in April and October as can Mexican Desert Primrose.
Plant winter veggies. Go for a hike or three.
November
Temperatures can fluctuate widely this month, but it is mostly a pleasant month of 70’s and 80’s. This is a actually a good time for visitors if you have been thinking about visiting Southern Arizona. It is usually dry and warm.
December
We may get a frost this month, but more times than not, we will just get the opening of the 2nd rainy season of the year. And when we say “Rainy Season” we are talking 6 inches, total, over the next two months. The rains are predominately gentler than the monsoon rains, ground soaking Oregon rains are not uncommon. With an ample amount of these rains and we will look forward to a beautiful wildflower season.
