After a historically dry winter, southern Utah is counting on the summer monsoon season to deliver some much-needed rain. And the latest forecast offers a glimmer of hope.
The seasonal outlook from the National Oceanic and Atmospheric Administration shows a slightly above-average chance the St. George area will get an active monsoon season that starts early, possibly before the end of June.
“Our outlook this year is driven primarily by the dry soils,” said Jon Meyer, assistant state climatologist with the Utah Climate Center. “That's a really good indicator for [the] earlier arrival of the monsoon weather pattern.”
While Utah’s parched soils may be bad for snowpack runoff and wildfire risk, Meyer said they also allow the ground to heat up quickly. Paired with June’s expected above-average temperatures, the surge of warmth could kick-start summer storms.
If the forecast becomes a reality, it would be welcome news for southern Utah, which has the state’s worst drought conditions.
“At this point, we're just going to really cross our fingers that all those ingredients align, and we do have a decent number of days where those moisture plumes are transported into our portion of the desert Southwest,” Meyer said.
Monsoon patterns are notoriously difficult to predict, though.
The storm systems originate hundreds of miles to the south in Mexico’s Gulf of California. In order for Utah to benefit, that ocean moisture needs to get funneled north along the Sierra Madre Occidental mountains. Then, depending on the position of the West’s dominant high-pressure system, that moisture may be pumped farther into Utah or be cut off entirely.
“It's this incredible symphony of meteorological ingredients that all plays together,” Meyer said. “And when it all plays harmonically together, central and northern Utah get a couple of days of high humidity and thunderstorms.”
Forecasters also have one less climatic signal to work with. The El Niño and La Niña cycle is in a neutral phase this summer. This in-between state brings some extra unpredictability to North American weather forecasts. Still, meteorologists are fairly confident that Mexico and Arizona will experience above-average monsoon activity, and southern Utah could easily piggyback on that.
The outlook for northern Utah, however, points toward below-average rain through August. Meyer described central Utah’s summer rain chances as a flip of the coin.
There’s so much variability from one monsoon season to the next, he said, that looking at historical average rainfall totals isn't helpful. Some years, the monsoon doesn’t show up at all. In others, a one-day deluge brings enough rain to make up for weeks of dry weather. Utah experienced that dynamic in early June, when St. George received nearly half an inch of rain in one hour.
That storm wasn’t connected with the monsoon, Meyer said — it came from a tropical depression in the Pacific. But it shows the impact a stray storm or two can have on Utah’s overall water situation.
“Those are significant wild cards,” Meyer said. “It's kind of like getting an inheritance from a long-lost relative. You don't want to count on it for your budget, but when it happens, you feel pretty blessed.”
Summer downpours don’t typically help fill reservoirs because the rushing water carries too much sediment and debris. Still, getting relief during the hottest time of year can go a long way toward keeping evapotranspiration in check and saturating Utah’s dry soils.
“Any amount of precipitation helps to improve our water situation,” said Utah Division of Water Resources Director Candice Hasenyager. “It's really important to get precipitation in all forms. We talk a lot about snow, but rain is important, too.”
Another benefit of an active monsoon season is that it can reduce demand for water at homes and farms — if Utahns remember to shut off their sprinkler systems when it rains.
That’s why the state offers rebates to help residents install smart irrigation controls that automatically shut off scheduled watering when rain is in the forecast, Hasenyager said. Utah also sends out weekly county-level recommendations for how often people should irrigate their lawns.
After a disappointing winter snowpack and with this summer’s monsoon still uncertain, Hasenyager said now is the time for Utahns to pay attention.
“If we're not getting these rains, I would imagine that the drought conditions will be exacerbated by higher temperatures, which increases demand,” she said. “So at the end of the day, we all just need to use our water as wisely as possible, because we just really don't know what's going to happen tomorrow.”
