Epidemiologists are divided on whether the dreaded second wave of COVID-19 will slam America as the weather gets cooler. Some say the ebbs and flows of the virus are normal. Others say that children returning to school and upcoming holidays such as Halloween and Thanksgiving can trigger a rise in cases, while still other experts paint a dire picture of dangerous surges of the virus in the upcoming months.

According to the Washington Examiner, several models had forecast a second wave of the virus. The Institute for Health Metric and Evaluation (IHME) produced a graph that shows a second wave beginning at the end of September and peaking around Thanksgiving.

The IMHE projection shows a “most likely” death toll of 1,907 Americans on Election Day— double the current toll — with numbers rising until early December, with peaks of 2,800 daily fatalities caused by the virus.

Epidemiologist Elli Klein at Johns Hopkins University said, “My feeling is that a second wave is coming, and it’s not so much whether it’s coming but how big it’s going to be,” she told The Washington Post. Some experts told the Post that they believe the second wave will not surge until after Election Day, November 3, cresting when fall gives way to winter.

These warnings come as the nation’s number of cases has fallen in recent weeks. But experts say that cooler, drier weather favors the viability of viruses and as the weather gets colder, people spend more time indoors which also escalates transmission, according to the Post.

Andrew Noymer, an epidemiologist at the Program in Public Health, University of California at Irvine, said the second wave will flow across the country.

“I firmly believe we will see distinct second waves, including places that are done with the first waves. New York, I’m looking at you,” he told the Post. “I expect fall waves starting in mid-October and getting worse as fall heads into winter and reaching a crescendo certainly after the election. Some places will peak around Thanksgiving, some places will peak around Christmas, some places not until January and February.”