2025 Monsoon Outlook for Southern Arizona

TUCSON, Ariz. (KGUN) — Monsoon is just around the corner and it’s time to reveal our 2025 Monsoon Outlook!

Before we get to the outlook, let’s take a look at some of the factors we consider when preparing our outlook. These factors vary from year to year based on the weather we have experienced leading up to monsoon.

This year, one of the factors is how dry it’s been ever since last August. Every month, from August through May, recorded below average rainfall which leads to extreme drought conditions.

Right now, southern Arizona is experiencing severe to extreme drought with the driest conditions being found south and east of Tucson. Such drought conditions lead to dry soil and this can play a role in how early monsoon develops.

We usually think of moisture when we think of monsoon, but really dry soil collects heat and reflects it back into the atmosphere above southern Arizona. As this heat rises into the atmosphere, it helps build the high pressure that eventually becomes the driving mechanism for monsoon.

Looking back through climate data, we often see an earlier start to monsoon when we have such dry conditions because the big dome of high pressure tends to develop earlier in June. Once this happens, the high pressure can move into a favorable position to draw moisture across southern Arizona and begin the monsoon thunderstorm cycle.

Another influence on our monsoon is the tropics. Tropical storms can have a big impact on our monsoon rain totals. If the moisture from the remnants of just one tropical storm makes it over southern Arizona, it can bring heavy rainfall over a 1 to 3 day stretch that can add lots of rain to our rain gauges.

This year, neither El Niño nor La Niña is in play as Eastern Pacific sea surface temperatures are close to average. So, in this ‘neutral’ state, we expect an average tropical storm season in the Eastern Pacific tropical storm zone.

This neutral pattern won’t have much of an effect on the Atlantic hurricane season, but the Atlantic is expected to be a bit more active than usual. There are a couple of reasons for this expectation. The first is because the Atlantic sea surface temperatures are running higher than average. This will tend to allow more storms to develop as they feed off of the warmer water.

The second reason we expect the Atlantic to be a bit busier is because there is little or no wind shear. Simply put, wind shear is varying wind directions as you go from the surface up through the atmosphere. With lots of wind shear, storms have a tough time staying organized and get torn apart.

Without much wind shear, storms have an easier time growing and maintaining their strength. This could result in bigger, stronger hurricanes that survive the trip across the Atlantic and eventually across the Gulf of America, which could bring more moisture into northern Mexico and southern Arizona.

Now we look at the long-range weather outlooks generated by the Climate Prediction Center. These models take us through August and show a slightly above average chance for rain for much of Arizona, including Tucson, Nogales and Sierra Vista.

Looking at the long-range temperature outlook, the Climate Prediction Center is indicating above average temperatures through the summer which is no big surprise. Above average temperatures are expected for all of the Desert Southwest with most of Utah favored to see temperatures running well above average.

Remember, the 2024 monsoon got off to a great start and stayed quite active through July. At that point, we were thinking the 2024 monsoon was going to be a dandy! That’s until August arrived and it seemed as though someone shut off the water valve and monsoon never recovered.

Monsoon is critical to southern Arizona’s annual rainfall and resulting water supply. In Tucson, we generally receive over half of our annual average rainfall during monsoon. Plus, despite the wind damage and flood risk, monsoon is an exciting time of year and can provide us all with some beautiful sights!

So, with that said, it’s time to reveal our 2025 Monsoon Outlook. When we look at all of the factors discussed and compare those to history, we predict that most of us will see slightly above average rainfall along with above average temperatures.

No matter the outcome, we wish all of you a safe and productive monsoon!