A powerful cross-country storm is set to sweep the United States from coast to coast, bringing flooding rain, mountain snow and the threat of severe storms to as many as 35 states over Halloween weekend and into Election Day week. Forecasters say the system, fuelled by El Niño, will start in the Southwest on Friday, October 30, 2026, and keep moving east for days, disrupting Halloween plans in California, soaking the Plains and Midwest by Election Day, and finally reaching the I-95 corridor by late next week.

The cross-country storm is not a single day of bad weather. It is a slow-moving, multi-stage event: heavy rain first in Texas, New Mexico and the Southwest, snow in the Sierra and the Rockies, then a renewed severe-weather threat from Texas into the Southeast as Election Day approaches. With nearly 40 million Americans facing a flash-flood threat at one stage of the storm alone, officials are urging people to watch forecasts closely, never drive through flooded roads, and build extra time into weekend travel.

Key Points

• A cross-country storm could deliver dangerous weather to 35 states, starting in the Southwest on Friday and reaching the East Coast late next week.
• The National Weather Service has a flood watch through Friday afternoon for much of west Texas and southeast New Mexico, with more than 3 inches of rain possible in the heaviest bands.
• Southern California faces moderate-to-heavy soaking rain by Saturday, threatening Halloween plans in Los Angeles and San Diego, where measurable Halloween rain is rare.
• Up to 5 inches of rain could fall from Phoenix to Flagstaff through Monday, and the southern Rockies could see 12 to 18 inches of snow.
• Nearly 40 million Americans are under a level 1 out of 4 flash-flood threat from Texas to Wisconsin on Monday, with severe storms possible from Texas into the Southeast on Tuesday and Wednesday.

What Happened

The forecast took shape on Thursday, October 29, when forecasters warned that November would begin with a bang. A strong upper-level low sitting near the Pacific Northwest coast is set to pivot a well-defined, strong Pacific jet toward the Southwest, allowing a secondary low to develop and draw rich Pacific moisture into the region into Saturday.

That moisture is the engine of the first phase. Some rain was already expected to fall in Arizona ahead of the main event, setting the stage for additional rain later Saturday into Sunday. Southern California was forecast to see moderate-to-heavy soaking rain by Saturday, likely disrupting Halloween plans, especially in larger cities such as Los Angeles and San Diego.

The numbers underline how unusual some of this rain could be. In San Diego, there have been only nine Halloweens with measurable rain since 1850, with the most recent in 1987. A wet Halloween in 2026 would therefore be a genuine rarity for the city, not just an inconvenience for trick-or-treaters.

At the same time, the National Weather Service warned Texas and New Mexico directly. A flood watch was in effect through Friday afternoon for much of west Texas and southeast New Mexico, where heavy rain was expected. The agency said: "A Flood Watch continues through Friday afternoon for much of west TX and southeast NM where heavy rain is expected. Rainfall totals could exceed 3 inches in the heaviest bands of rain across the southern TX panhandle to the Big Bend region."

Earlier in the week, the National Weather Service had already issued a flood warning for Arizona, California, Colorado, Kansas, Nevada, Oklahoma and Utah, putting those states on high alert before the main system even arrived.

Background and Context

Cross-country storms of this kind are driven by the position of the jet stream, and this one has an extra push from El Niño. Forecasters say El Niño is helping steer the Pacific jet stream over the southern tier of the country, which is why moisture from the Pacific is being funnelled so efficiently into the Southwest and then carried eastward.

The Southwest is the first region to feel the full force. Through Monday morning, the system was expected to push inland, spreading rain eastward and delivering widespread totals of 1 to 2 inches or more across portions of Arizona. From Phoenix to Flagstaff, up to 5 inches of rain could fall through Monday, according to the FOX Forecast Center.

That matters because the ground in parts of Arizona is already wet. Flagstaff had already recorded 5.69 inches of rain so far in October, and forecasters warned that if an additional 3 inches fell as forecast, significant flash flooding could occur. A level 2 out of 4 flash-flood threat was in effect through the whole weekend in the region.

In the higher elevations, cold air was expected to become trapped, producing snow from the Sierra to the Rockies. The southern Rockies were forecast to see the highest snow totals, between 12 and 18 inches, a sharp contrast with the flooding rain at lower elevations.

The pattern is familiar in one respect: autumn in the United States often brings powerful systems that cross the whole country, changing character as they go. What makes this one stand out is its reach, with dangerous weather possible in 35 states, and its timing, spanning Halloween weekend, the end of daylight saving time and the run-up to the November 3 midterm elections.

Cross-Country Storm Timeline: From California to the East Coast

Friday, October 30, is the opening act. Heavy rain is expected in west Texas and southeast New Mexico under the flood watch, while showers and isolated thunderstorms develop in Arizona, especially south of the Mogollon Rim and toward the Phoenix foothills. In the Northeast, by contrast, Friday was expected to be mild, with a moisture-starved cold front bringing only clouds and possibly a sprinkle or two.

Saturday, Halloween, is when Southern California takes centre stage. Moderate-to-heavy soaking rain was forecast for the region, with Los Angeles and San Diego most at risk of disrupted plans. South Florida, meanwhile, was expecting increased rain chances, with a 50 percent chance of rain at 6 p.m. Saturday in Miami, 65 percent in Fort Lauderdale and 60 percent in West Palm Beach, and stormier conditions on Sunday and Monday with frequent lightning, gusty winds and locally heavy rain possible.

Sunday brings a second rain event to Arizona. Forecasters in Phoenix described two rain events separated by a mostly quieter Saturday, with the second system bringing a stronger subtropical moisture plume and a potentially longer period of light to moderate rain, especially across central and eastern Arizona. Sunday's rain could compound problems from Friday's event, particularly in terrain northeast of Phoenix where air rising over slopes can enhance rainfall.

By Monday, the storm pushes into the Plains and Midwest. Nearly 40 million Americans were placed under a large level 1 out of 4 flash-flood threat from Texas to Wisconsin on Monday, and heavy rain could increase the risk of flash flooding across the Plains. A new area of low pressure across the Plains was expected to form, allowing warm, moist air to stream in ahead of it.

Tuesday into Wednesday is the severe-weather window. Warm air interacting with an approaching cold front may allow severe storms to develop along it from Tuesday into Wednesday, with the atmosphere becoming primed and energised for severe storms from Texas into parts of the Southeast by early week through midweek. Forecasters cautioned, however, that models disagreed on where exactly the area of low pressure would form and how strong it would become, so the precise severe-weather zone remained uncertain.

From Wednesday onward, the storms continue moving into the East, potentially bringing heavy rain Thursday and Friday to major cities on the I-95 corridor. 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.

Reactions and Quotes

The National Weather Service's flood watch for Texas and New Mexico was blunt about the risk: "Rainfall totals could exceed 3 inches in the heaviest bands of rain across the southern TX panhandle to the Big Bend region." The agency paired the watch with safety advice that applies across the whole storm track.

Its guidance urged people to stay away from flood-prone areas such as stream beds, drainage ditches and culverts during heavy rain, to move to higher ground if flooding threatens, and to remain alert in flood-prone areas. It warned people to be especially cautious at night, when it is harder to recognise flood dangers.

The most important message, repeated by forecasters in every flood event, was about driving: "Never drive your car into water of unknown depth. Most flash flood deaths occur when people drive their vehicles into flood waters." The agency's slogan sums it up: "Turn Around Don't Drown!! If your vehicle stalls, abandon it immediately and seek higher ground. Flood water may rise quickly, cover the vehicle and sweep it away."

Forecasters were also honest about what they did not yet know. The FOX Forecast Center stressed that the forecast remained uncertain about where severe storms would develop, because forecast models disagreed on where exactly the area of low pressure would form and how strong it would become. That uncertainty is a reason to check updated forecasts daily rather than relying on a single outlook issued days in advance.

Why It Matters

A storm touching 35 states matters because it hits almost every part of American life at once. Halloween is one of the biggest outdoor nights of the year for families, and soaking rain in Southern California, storm chances in South Florida and a mild but dry Northeast mean the trick-or-treating forecast will look completely different depending on where you live.

It also matters for travel and safety. Flash flooding is one of the deadliest weather hazards in the United States, and it often kills people in cars, not in homes. With more than 3 inches of rain possible in parts of Texas and New Mexico, up to 5 inches in the Phoenix-to-Flagstaff corridor and a level 2 out of 4 flash-flood threat through the weekend in Arizona, the risk is not theoretical. Desert washes, low-water crossings and normally dry stream beds can become dangerous quickly.

Then there is Election Day itself. The storm is forecast to move into the Plains and Midwest on Monday and bring a severe-weather threat from Texas into the Southeast on Tuesday and Wednesday, right as voters head to the polls on November 3. Heavy rain and severe storms do not stop elections, but they can slow travel to polling places, complicate outdoor campaign events and strain local emergency services. Election officials and voters alike will need to plan around the weather, not ignore it.

Finally, the storm is a reminder of how El Niño can reshape an entire season. By steering the Pacific jet stream over the southern United States, it can deliver repeated rounds of moisture to regions that are often dry in autumn, turning a single storm into a week-long, coast-to-coast event.

What Happens Next

In the short term, the key dates are Friday through Monday. The Texas and New Mexico flood watch runs through Friday afternoon, Southern California's soaking rain arrives by Saturday, Arizona faces a second round of rain late Saturday into Sunday and through Monday, and the Plains and Midwest flash-flood threat peaks on Monday.

After that, attention shifts to the severe-weather window on Tuesday and Wednesday, when forecasters will narrow down where the low-pressure system forms and which parts of Texas and the Southeast face the greatest risk. Updates through the weekend and into early next week will be critical, because the models still disagree on the details.

By late next week, the focus moves east. Heavy rain is possible Thursday and Friday along the I-95 corridor, from Raleigh to Washington, New York and Boston, ending a nearly two-week dry stretch for those cities. Anyone travelling for Election Day or the weekend after should expect the storm's effects to linger well beyond Halloween.

For now, the advice is simple: check your local National Weather Service forecast before travelling, avoid flooded roads at all costs, allow extra time for Halloween and Election Day plans, and keep an eye on updates as this cross-country storm evolves.

Frequently Asked Questions

How many states will the cross-country storm affect?

Forecasters say the powerful storm could deliver dangerous weather to 35 states across the country, starting in the Southwest and moving east through Election Day week and beyond.

Where is flooding most likely?

West Texas and southeast New Mexico are under a flood watch through Friday afternoon, with more than 3 inches possible in the heaviest bands. Arizona also faces a level 2 out of 4 flash-flood threat through the weekend, with up to 5 inches possible from Phoenix to Flagstaff.

Will Halloween plans be affected?

Yes, in some regions. Southern California faces moderate-to-heavy soaking rain by Saturday that could disrupt Halloween plans in Los Angeles and San Diego, while South Florida faces increased rain and storm chances. The Northeast, by contrast, was expected to stay mostly dry for trick-or-treating.

How much snow is expected?

Snow is forecast from the Sierra to the Rockies, with the southern Rockies seeing the highest totals, between 12 and 18 inches.

Could the storm affect Election Day?

The storm moves into the Plains and Midwest on Monday, and severe storms are possible from Texas into the Southeast on Tuesday and Wednesday, around the November 3 midterm elections. Voters should check local forecasts and allow extra travel time.

Related coverage on US News Pulse: Thunderstorms Hit 19 States Today as NWS Warns of Heavy Rain, Wind and Hail, Phoenix Halloween Rain Forecast: First Wet October 31 in Nearly 40 Years, and Western US Winter Storm Brings Up to 14 Inches of Snow Before Halloween.