August heat leads a hotter-than-normal monsoon at Phoenix Sky Harbor

The 2026 monsoon left Phoenix hotter than normal but not much wetter. From June through September, Sky Harbor averaged 2.8°F above its 1991–2020 normal temperature.

Rainfall, meanwhile, landed almost exactly where a typical year would put it. The airport gauge caught 2.5 inches over the stretch, against a normal of 2.4 inches. The gap rounds to 0.0 inches.

Compared with last year, the summer was both warmer and drier. Sky Harbor ran 0.7°F warmer than June through September of 2025. Rainfall fell short of the 3.2 inches recorded last year, a difference of -0.8 inches.

For people who lived through it, the numbers back up what many felt. Heat was the main story of this summer in the Valley, and much of the rain arrived near the end.

Every month ran hot

Each month of the season finished above its normal temperature. August stood out the most, at 4.1°F above normal. June was close behind, at 3.6°F above.

July came in 1.9°F above normal, and September finished 1.4°F above. Even the mildest month of the stretch was warmer than a typical year.

The early heat was sharper than last year's. June 2025 ran 2.2°F above normal, while June 2026 ran 3.6°F above. Across the season, 2026 matched or topped the same months of 2025.

Other reporting points the same way. KJZZ reported that Phoenix's June-through-August average this year tied 2023 in the city's hottest-summer rankings, just behind the top spot (kjzz.org).

The rain came late

Rainfall told a more uneven story from month to month. June and August finished essentially at their normals. June's difference rounded to -0.0 inches, and August's to 0.0 inches.

July came up short, finishing -0.5 inches against its normal. September made up the gap, coming in 0.5 inches above normal with 1.1 inches of rain at the airport.

That late push carried the season. September supplied 1.1 inches of the season's 2.5 inches at Sky Harbor. Dan Henz of the Flood Control District said September made up a large share of the rain received this season (azfamily.com).

Reporting tied the late rain to tropical moisture. The Copper Courier reported that rain from Hurricane Polo pushed official totals just over the line for an average monsoon (coppercourier.com).

The outlet also reported that the strong El Niño played a part in moving moisture from former cyclones Marie and Polo (coppercourier.com). That moisture showed up in the air over Phoenix.

In mid-September, the National Weather Service measured a record high amount of moisture in the atmosphere for that time of year, based on Phoenix records (weather.gov). In its write-up of those storms, the agency said its Phoenix warning area had not seen a Moderate Risk since 2023 (weather.gov).

Last year leaned on September too, and leaned harder. Sky Harbor collected 2.3 inches in September 2025, compared with 1.1 inches this September. That lighter finish is the main reason 2026 trailed 2025 overall.

The 2026 season did get more rain than 2025 in July and August. But a dry June and a lighter September left it behind last year's total.

Beyond the airport

Sky Harbor is the official Phoenix record, but it is one gauge at one spot. A season-end tally by the Copper Courier, counting June 15 through Sept. 30, also put the airport just barely over average (coppercourier.com).

Across the wider county, the season looks wetter. Preliminary figures reported by azfamily show the countywide average finishing well above its typical benchmark (azfamily.com).

That means some neighborhoods, from the West Valley to the East Valley, likely saw very different totals than the airport. A storm can soak one part of town and miss another entirely.

The final figures could shift slightly as the weather service reviews its records. Watch for the official monsoon summary and for fall temperatures, which will show whether this summer's heat finally eases.

How we did this

We used official monthly average temperature and rainfall records for Phoenix Sky Harbor for June through September of 2025 and 2026, and compared each month with its 1991–2020 normal. The seasonal temperature gap of 2.8°F is a simple average of the monthly differences, and seasonal rainfall is the sum of the monthly totals, compared with a normal of 2.4 inches.

Normal: the 1991–2020 average for a given month at Phoenix Sky Harbor, used as the benchmark for a typical year. Monsoon: Arizona's summer storm season. This report counts June through September. Average monthly temperature: a measure that combines daytime highs and overnight lows across the whole month.

Limitations

• Sky Harbor is a single gauge. Rainfall in the monsoon is patchy, so your neighborhood may have been much wetter or drier than the airport.
• Our season counts full months from June through September. The official monsoon window starts June 15, so season-end totals from other sources differ slightly from ours.
• Recent monthly figures can be revised, and the countywide rainfall figures cited here are preliminary.
• Small differences are rounded. A rainfall gap shown as zero means the season was very close to normal, not exactly equal.
• The temperature and rainfall records show what happened, not why. Explanations for the late rain come from the news reports cited.

Sources

• NOAA National Centers for Environmental Information: Monthly weather summary (Global Summary of the Month): USW00023183, latest period September 2026; retrieved Oct. 12, 2026. Data
• NOAA National Centers for Environmental Information: Monthly climate normals, 1991–2020: USW00023183 (1991–2020 U.S. Climate Normals), latest period 2020; retrieved Oct. 12, 2026. Data
• NOAA National Centers for Environmental Information: Daily weather observations (GHCN-Daily): USW00023183, latest period 2026-10-07; retrieved Oct. 12, 2026. Data