How far West does the monsoon season extend? (Phoenix, Tucson: bars, beaches)

[cBach]

I find it interesting that the desert Southwest (AZ/NM/NV) has their "rainy season" in the summer but CA has their rainy season in the winter. Where is the divide for this? For example, I know Los Angeles and San Diego have dry summers and rainy winters, but what about Palm Springs? What about Barstow? Needles?

Is there a place that has both rainy winters and rainy monsoonal summers (if you think of a Venn diagram, there should be some overlap where the rainy summers and rainy winters overlap). If so, where is that?

Also, is there anyplace in AZ where the rainy winter weather from CA can hit on a regular basis?

Obviously, I use the word "rainy" sparingly. The rainy season in AZ would be classified as the dry season anywhere else in the US. The rainy season in CA is actually pretty healthy though.

[beTucsonan]

Basically speaking, climate events cause wind streams which pull moisture North/Northeast out of the Sea of Cortez (Gulf of California) or North/Northwest out of the Gulf of Mexico. The western edge of this pattern is typically (and roughly) equated to the mountains which form the Great Basin Continental Divide (Continental divide - Wikipedia, the free encyclopedia), but coastal cities such as San Diego have been known to experience monsoon pattern storms as well, when conditions are right.

Obviously, the amount of rainfall associated with the monsoon season is not much in contrast to the amount of rain some parts of California receive, so it's not typically considered a part of a rainy season for residents of that state. Compare that to places like Tucson where the average rainfall of 11 inches or so is about a quarter of the national average and you can see why even a relatively minor "rainy season" gets so much attention there.

[observer53]

Our winter rain storms do come from California. The weather patterns are completely different that time of year, compared to the monsoon season when it comes up from the south.

[borregokid]

Arizona actually has two rainy seasons July, August and September and December, January and February. If you look at the whole Sea of Cortez and the proximity to Arizona and the higher elevations in Arizona you can see why Arizona gets more rain. Borrego Springs has been know to get monsoonal rains and flash flooding. BS is in a rain shadow as is most of the California-Mohave Desert. Once you cross over the Colorado River on highway 10 to Quartzsite you can tell you have left the Colorado Desert and are now in the Sonoran desert. The first thing you will notice is a few Saguaro cactus and the creosote plants arent all dried out. You have also gained some elevation. Blythe in California is 300 feet and Quartzsite in Arizona is 900 feet. About 10 miles outside of Yuma you start picking up a little elevation and you will notice the desert is greener traveling on interstate 8. By the time you get to Picacho Peak you will notice you are in the "lush" Sonoran desert.

The same storms that hit California in the winter time usually track all the way to Arizona whether they bring rain or not is questionable. Typically though if a storm is strong enough to bring rain to the California desert in 24 hours or so it will hit Phoenix and Tucson with rain. If you want to look at a good winter rain year in all of the SW 2005 had consistent rain in January-March raining almost every week.

[Gandalara]

In the summer, I get email or a text from a friend in AZ, "You have humidity coming!"
In the winter, I send email or a text to my friend in AZ, "You have a storm coming!"

[Valley Native]

Originally Posted by cBach

I find it interesting that the desert Southwest (AZ/NM/NV) has their "rainy season" in the summer but CA has their rainy season in the winter. Where is the divide for this? For example, I know Los Angeles and San Diego have dry summers and rainy winters, but what about Palm Springs? What about Barstow? Needles?

Is there a place that has both rainy winters and rainy monsoonal summers (if you think of a Venn diagram, there should be some overlap where the rainy summers and rainy winters overlap). If so, where is that?

Also, is there anyplace in AZ where the rainy winter weather from CA can hit on a regular basis?

Obviously, I use the word "rainy" sparingly. The rainy season in AZ would be classified as the dry season anywhere else in the US. The rainy season in CA is actually pretty healthy though.

As was mentioned by another poster, Arizona has two main precipitation seasons. The winter season (December through March) is actually the primary wet season, and it's the one that really matters the most because of the snowfall in the high country that creates a snowpack for spring runoff. This is one of the things we count on for water supplies. Also, if you look at Phoenix's rainfall averages for the year, there is actually more rain that falls during the winter rainy season than during the summer monsoon. Tucson, on the other hand, tends to get more rain during the summer.

Although southern CA does have a distinct winter rainy season, even their winters are not all that wet compared to northern CA, or the Pacific NW. Their average winter brings in a fair share of Pacific storm systems, but there is also a fair share of sunny weather too. In most cases when there is a major storm system that affects southern CA, Arizona receives a good share of the precipitation from it the following day. On the other hand, most of the monsoon storms that affect AZ are rather scarce in southern CA.

I would say that during a monsoon with a strong flow of moisture from the east or SE, a large part of the southern CA deserts can be affected. Blythe, Needles, Imperial, El Centro, and the Palm Springs area do receive some rain during July & August, but it tends to be very sporadic. The L.A area had a freakish monsoon storm a week or so ago when lightning struck some people on the beaches ... so even L.A & San Diego can get monsoon moisture once in a while if the flow is strong enough.

As far as the dividing line between regions that receive more precipitation in the winter than in the summer: I would say that falls somewhere east of the Phoenix metro area. Perhaps Globe, Superior, or somewhere like that will get an equal share of precipitation in both the summer & winter. Phoenix averages more in the winter, but Tucson and all of eastern/SE Arizona have abundant summer rainfall. The White Mountains in particular can get thundershowers on a daily basis during July & August.

[rambrush]

You also have to take into account that the Monsoon moisture does go North into Montana etc.

[cacto]

I have been in summer t-storms as far west as where Maricopa and La Paz counties meet, maybe close to the Colorado. I've never heard of summer rain in the Mojave.

[Fiddlehead]

I would say the western Mogollon rim would get the most winter and summer ppt. Places Like Williams, Prescott, and Flagstaff.
They capture monsoon moisture com I n from the south in summer and winterror storms as well. In both cases or graphic effec are important.

[mojavesue]

Well folks it is 10:00 pm here in Barstow, CA 60% humidity and 92 degrees. It was 105 today. I looked this up and apparently it is scheduled all week to a degree. Water coolers do not work properly in humid and hot weather combos. If anyone has been through this place on the way to Las Vegas,NV. I am sure its a quick jump back into their cars with air conditioning. My half-brother described the summer weather as "a blast furnace" as he exited his car. I will continue to whine until the weather turns hopefully before Halloween. The dogs have voted for "Alaska"; one is a chow. I always say 40 degrees is my favorite.