Sales of previously owned US homes fell in January by the most in nearly four years, a month marked by historically cold temperatures and a massive winter storm.

Contract closings decreased 8.4% to a 3.91 million annualized pace in January, according to National Association of Realtors data released Thursday. That was below the median forecast of economists surveyed by Bloomberg.

An extensive winter storm in late January that blanketed much of the US with snow and ice may have delayed many contract closings. In the hard-hit South, the nation’s biggest home-selling region, sales slumped 9% to an annualized pace of 1.81 million. Closings also fell sharply in the rest of the country.

“The below-normal temperatures and above-normal precipitation this January make it harder than usual to assess the underlying driver of the decrease and determine if this month’s numbers are an aberration,” NAR Chief Economist Lawrence Yun said in a statement.