A sprawling, El Niño-fueled storm is about to cross the entire United States, bringing heavy rain, mountain snow, flash flooding and severe weather to as many as 35 states over the coming week, according to forecasters. The system arrives in the Southwest in time for Halloween weekend, reaches the Plains and Midwest by Election Day, and is expected to push into the East Coast by late next week — a coast-to-coast journey that could disrupt holiday plans, travel and even voting.
The forecast, published by FOX Weather on October 29, describes a powerful storm that will deliver what the outlet calls dangerous weather to 35 states across the country. It is driven by a strong upper-level low near the Pacific Northwest coast that will pivot a well-defined Pacific jet stream toward the Southwest, drawing rich Pacific moisture inland. A second low-pressure system will then develop, feeding that moisture into the Southwest through Saturday and setting the stage for a week of unsettled weather nationwide.
A Halloween Weekend Soaking in the West
California and the Southwest will feel the storm first. Some rain will fall in Arizona ahead of the main event, with additional rain arriving later Saturday into Sunday. Southern California is expected to see moderate-to-heavy soaking rains by Saturday, which forecasters warn could disrupt Halloween plans, especially in larger cities such as Los Angeles and San Diego.
The timing is unusual for San Diego. According to FOX Weather, the city has recorded measurable rain on only nine Halloweens since 1850, with the most recent rainy Halloween coming in 1987. This year, trick-or-treaters in Southern California may need rain gear instead of just costumes.
The rainfall totals in Arizona could be significant. Through Monday morning, the system is expected to spread rain eastward across the Southwest, bringing widespread totals of one to two inches or more across portions of Arizona. From Phoenix to Flagstaff, up to five inches of rain could fall through Monday, according to the FOX Forecast Center.
That matters because the ground in northern Arizona is already saturated. Flagstaff has recorded 5.69 inches of rain so far in October, and forecasters warn that if another three inches falls as expected, significant flash flooding could occur. A level two out of four flash flood threat is in effect through the whole weekend in the Southwest.
The National Weather Service has also warned of heavy rain farther east. A flood watch was in effect through Friday afternoon for much of west Texas and southeast New Mexico, where rainfall totals could exceed three inches in the heaviest bands from the southern Texas panhandle to the Big Bend region, the weather service said on October 29.
Snow in the High Country
While the lowlands deal with rain, the mountains will deal with snow. As cold air becomes trapped in the higher elevations, snow is expected to fall from the Sierra Nevada to the Rockies, forecasters say.
The southern Rockies are expected to see the highest snow totals, between 12 and 18 inches. That kind of snowfall in late October and early November can make mountain passes treacherous, and drivers heading through the high country this weekend should expect winter driving conditions, including slick roads and reduced visibility.
The snow is part of the same system, not a separate storm. The cold air aloft, combined with the Pacific moisture streaming inland, creates the classic setup for heavy mountain snow on the cold side of the storm while rain falls at lower elevations.
The Storm Marches Into Election Day
Later Monday, the storm will begin to move into the Plains and Midwest. Heavy rain could increase the risk of flash flooding across the Plains, and nearly 40 million Americans are under a large level one out of four flash flood threat from Texas to Wisconsin on Monday, according to the FOX Forecast Center.
Ahead of the storm, a new area of low pressure across the Plains will likely form, allowing warm, moist air to stream northward. That warm air will then interact with an approaching cold front, which may allow severe storms to develop along it from Tuesday into Wednesday.
That timing puts the storm squarely over the central United States on Election Day, Tuesday, November 3. CNN reported on October 28 that a soggy storm will track through the central United States on Election Day and could influence voter turnout for key races in the region. Confidence is growing for widespread rain from parts of the Great Lakes and Upper Midwest to the western Gulf Coast on Tuesday, though exactly who gets the most disruptive soaking is still in question.
According to CNN's forecast analysis, parts of Iowa, Kansas, Michigan, Texas and possibly Ohio could contend with wet conditions on Election Day. Gusty winds could also accompany the rain in the Midwest and Plains. Severe thunderstorms and heavy rain are possible threats on the storm's southern side, from Texas to the lower Mississippi Valley.
The forecast remains uncertain about where severe storms will develop, forecasters caution, because weather models disagree on where exactly the area of low pressure will form and how strong it will become. Regardless, the FOX Forecast Center said the atmosphere is becoming primed and energized for severe storms from Texas into parts of the Southeast by early in the week through midweek.
What This Means
For voters, the storm adds a weather wrinkle to an already high-stakes midterm election. Rainfall and other active weather tend to suppress voter turnout, while sunshine has the opposite effect, according to multiple studies cited by CNN. That could matter in a year when more than 39 million people have already cast ballots through early voting, leaving millions more expected to vote on Election Day itself.
For travelers, the storm is a week-long headache rather than a single bad day. The system moves slowly, bringing rain to one region after another, and its hazards change as it travels: flash flooding in the desert Southwest, heavy snow in the Rockies, severe storms in the Plains and South, and finally heavy rain in the East.
For residents of the Southwest, the most immediate danger is water, not wind. Flash flooding in desert terrain can develop quickly, especially in areas that have already received heavy October rain. Forecasters urge people in flood-prone areas to avoid driving through flooded roads and to pay attention to flood watches and warnings, which carry different levels of urgency.
The storm also fits a broader pattern this autumn. Forecasters link the active Pacific jet stream to El Niño, which is helping steer storms over the southern tier of the country. That same pattern has already delivered a wet October to parts of the West, and this storm could add substantially to monthly rainfall totals in Arizona and California before it moves on.
What Happens Next
From Wednesday onward, the storms will continue moving into the East, potentially bringing heavy rain Thursday and Friday to major cities on the I-95 corridor, according to FOX Weather. Locations from Raleigh, North Carolina, to Washington, D.C., New York City and Boston could all see rain for the first time in nearly two weeks.
By late next week, then, the storm will have touched nearly every part of the country: the West Coast and Southwest first, the Rockies with snow, the Plains and Midwest on Election Day, the South with severe weather, and finally the East Coast. It is the kind of coast-to-coast system that forecasters watch closely precisely because it affects so many people in so many different ways.
Forecasters caution that details will shift as the storm develops, especially the exact placement of the heaviest rain and the severe weather threat in the middle of the week. Anyone with travel plans, outdoor Halloween events or Election Day voting plans in the affected regions should check updated forecasts from the National Weather Service and local forecast offices as the storm approaches.
For now, the message from forecasters is consistent: this is a big, slow-moving, multi-hazard storm, and it is coming to nearly the whole country. Whether it brings rain on a Halloween costume, snow on a mountain pass, or a wet trip to the polling place depends on where you live — but very few Americans will escape it entirely.
Sources: FOX Weather, October 29, 2026; CNN, October 28, 2026; National Weather Service flood watch, October 29, 2026.
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