Phoenix is bracing for a rare weather anomaly this Halloween weekend, as two distinct rainfall events are expected to hit the Valley between Friday, Oct. 30, and Sunday, Nov. 1. While the rain threatens to dampen some festivities, a projected break in the weather on Saturday should keep most Halloween night plans intact, according to reporting from AZCentral.
This isn’t just a minor drizzle; it’s a statistical outlier. Phoenix hasn’t seen measurable rain on Halloween since 1988. For a city where the holiday is typically defined by 80-degree temperatures and dry air, the arrival of a strong low-pressure trough is shifting the script, bringing a welcome cool-down alongside the risk of flash flooding.
Friday brings the first wave of moisture
The first window of precipitation arrives Friday, Oct. 30. Moisture moving from the southwest is expected to sweep across the Valley, beginning in the morning and settling in by lunchtime. This isn’t the violent, severe weather that hit Arizona last week, but rather a consistent rain likely to produce between 0.25 and 0.75 of an inch.
The stakes here are primarily about infrastructure and safety. Because the rain is expected to be steady, the Weather Prediction Center has flagged central Arizona for a slight chance of flooding. Those in lower elevations between Phoenix and Tucson should be particularly cautious of scattered flash floods, as the ground may struggle to absorb the consistent volume of water.
For those heading out Friday, the advice is simple: bring a jacket. Highs will hover in the mid-70s, a sharp departure from the usual October heat.
An active period of weather will return later this week and through Halloween weekend. Although severe weather is currently not expecting, there could be periods of heavy rainfall, leading to a risk of flash flooding on Friday & Sunday. Stay tuned for further updates. #azwx #cawx pic.twitter.com/Jy1yLmpq3q
Halloween night offers a reprieve
If you’ve spent weeks planning an outdoor costume party or a neighborhood trick-or-treating route, there is good news. Saturday, Oct. 31, is expected to be largely free of rain. While the sky will likely remain mostly cloudy and isolated showers could pop up near the foothills or further north, the middle of the day should remain calm.
There is a caveat for the late-night crowd. As the window closes on Halloween, light rain chances could reappear by the evening. While pre-midnight activities are likely to stay dry, those staying out into the early hours of Sunday have a higher probability of encountering stray storms arriving ahead of the second major system.
An atmospheric river arrives Sunday
Sunday, Nov. 1, is slated to be the more significant rainfall day of the weekend. Unlike Friday’s tropical moisture from the Gulf of California, Sunday’s weather is being driven by a modest atmospheric river. This system will bring more traditional uplift and moisture from the southwest.
The impact will be felt most heavily in higher elevations and southeastern Arizona, but the Valley won’t be spared. Lower elevations could see an additional half-inch to one inch of rain, while the Mogollon Rim could see up to two inches. This cumulative moisture—hitting twice in three days—increases the risk of localized flooding in low-lying areas.
| Day | Expected High | Rain Probability/Type | Primary Risk |
|---|---|---|---|
| Friday, Oct 30 | Mid-70s | High (Consistent showers) | Scattered flash floods |
| Saturday, Oct 31 | Mid-70s | Low (Mostly cloudy) | Isolated late-night showers |
| Sunday, Nov 1 | Upper 60s | High (Atmospheric river) | Localized low-lying flooding |
The trade-off for the rain
While rain is usually a nuisance for holiday planners, the accompanying temperature drop is a rare win for costume wearers. In the last decade, Halloween temperatures in Phoenix have typically stayed in the 80s. This year, with highs in the 70s and lows in the mid-60s, the risk of overheating in heavy costumes is virtually nonexistent.
As the system clears out by Monday, Nov. 2, the city will be left with a cooler atmosphere and a rare memory of a wet Halloween. The only remaining question is whether the timing of the second wave holds steady or shifts early enough to clash with the Saturday night festivities.
Odds are becoming increasingly favorable for another period of wet unsettled weather across the Desert Southwest late this week into next weekend as moisture moves in ahead of a Pacific weather system. This means there is potential for a wet Halloween weekend. #azwx #cawx pic.twitter.com/6UvFIcyl1d
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