Flash flooding, heavy rainfall and tornadoes have forced election officials in three different regions across the United States to move polling locations, scrambling Election Day plans in hot-button races. At least seventeen polling locations were moved in five Florida counties — including Brevard County, Indian River County, St. Lucie County, Martin County and Palm Beach County — after intense rainfall caused flash floods on Monday and into Tuesday morning. Roads were impassable in several parts of the state’s Atlantic coast after a storm dumped as much as 22 inches of rain in 24 hours in a storm that “exceeded everyone’s expectations,” as one forecaster put it.

Severe storms were moving across Oklahoma, Texas and Arkansas overnight on Tuesday. Forecasters issued a tornado watch that lasted until about 2:45 a.m. local time on Tuesday. Forecasters were also predicting possible flash flooding in parts of Alabama, Tennessee, Arkansas and Mississippi on Tuesday, as that storm system continued to travel east. A flood watch remained in effect in some parts of Florida, though rainfall rates were slowing. “Areas affected by catastrophic flooding remain extremely sensitive to any additional rainfall,” forecasters wrote in a Tuesday morning forecast discussion.

In Oklahoma, a tornado on Sunday forced Cimarron County officials to change one of its polling locations. The tornado, which had peak winds of about 100 mph, snapped tree branches, damaged the roof of the Keyes Community Center and collapsed a wall, according to a damage survey report from the National Weather Service. In an emergency request, county election officials said the tornado caused “considerable structural damage” to the community center “rendering the polling location unsafe.”

And after historic flooding in the Four Corners region, Utah Lt. Gov. Deidre M. Henderson declared a state of emergency and issued a special accommodation that will allow voters registered in San Juan County who are isolated by floodwaters to request and return ballots electronically. The Colorado Secretary of State is allowing a similar measure for voters — allowing votes online — in La Plata and Archuleta counties, according to 9 News. More election day surprises could be in store. Experts say inclement weather has suppressed voter turnout in past elections.

In research of elections from 1948 to 2000, researchers observed a modest drop in turnout during unusually intense rain storms. “What we found was that for every inch of rain that a county received above its average amount of rainfall, voter turnout went down about eight-tenths of 1 percentage point,” said Brad Gomez, an associate professor of political science at Florida State University. But experts said the effect of rain on turnout is diminishing over time as more people choose to vote early or vote by mail, and they said it’s hard to predict what effect the inclement weather will have, if any, on key races.

In Florida, Gov. Ron DeSantis declared a state of emergency in seven counties along the Atlantic seaboard that are being hit with flash flooding and extreme precipitation. Damage in parts of Colorado remains widespread after heavy rain and flooding, with first responders searching for people who may be stranded across the area, including by helicopter. People with homes along the Animas River in southwestern Colorado were also facing evacuation. Record rainfall was also reported in usually dry Arizona, causing deadly flooding and power outages.

The brief closure of two voting centers in the state’s Maricopa County sparked a chorus of conspiracy insinuations online Monday. Two out of the 254 polling locations in the county had to be temporarily shuttered “due to power related issues,” election authorities announced on social media.

The two polling locations have since been reopened, authorities said, but some online used the shutdown to allege impropriety in the competitive swing state. Arizona Gov. Katie Hobbs issued a statewide emergency declaration on Monday after recently issuing an emergency for Navajo and Coconino counties. The governors of New Mexico and Colorado also asked President Donald Trump to declare a major disaster to receive federal funding assistance.

Rain is also expected to hit the central U.S. as voters head to the polls there Tuesday, but experts said the impact on the election outcome is expected to be minimal. The weather’s effect on voter turnout will be watched closely by campaigns seeking to draw as many supporters as possible to polling places. The storm system will move east Tuesday, with heavy rain possible in Mississippi, Missouri and western Tennessee. On Election Day, “scattered flash floods are possible” in the lower Mississippi River valley and into areas such as Memphis, Tennessee, said Jennifer Tate, a meteorologist with the National Weather Service Weather Prediction Center in College Park, Maryland.

Much of the rest of the central U.S. — from East Texas to the Midwest — can expect wet, dreary weather on Election Day. Election Day weather on the West Coast looks mostly pleasant, with pockets of rain in Northern California. Outside of Florida, the East Coast looks clear, though some rain is expected in Maine.