Edmunds, the leading car shopping and information platform, forecasts that 1,317,738 new cars and trucks will be sold in the U.S. in October, for an estimated Seasonally Adjusted Annual Rate of 17.6 million. This reflects a 13.3 percent decrease in sales from September 2017 and a 3.5 percent decrease from October 2016. 

Edmunds analysts say that while sales continue to be slower this year compared to 2016, if incentives can entice enough car buyers to clear out the high levels of 2017 inventory then the year should still finish historically strong.

"A 17.6 million SAAR in October is expected to be the second highest monthly sales rate of 2017, so despite the year-over-year decline, the industry can still consider it a solid month," said Jessica Caldwell, Edmunds executive director of industry analysis. "We expect to see increasingly aggressive incentives offered on outgoing models through the end of the year as automakers look to build on this momentum, so car buyers can likely anticipate some door-buster deals this holiday season." 

October sales are also expected to experience a continued lift from shoppers impacted by this summer's hurricanes. 

"While replacement demand in Houston was higher in September, we anticipate that hurricane recovery efforts will continue to supplement October vehicle sales in the market," Caldwell said. "In Florida, far fewer vehicles were lost to flood damage, but we expect to see an incremental boost in vehicle sales primarily from shoppers who may have delayed their purchases due to the storm."

Edmunds estimates that retail SAAR will come in at 14.6 million vehicles in October 2017, with fleet transactions accounting for 17.1 percent of total sales. An estimated 3.2 million used vehicles will be sold in October 2017, for a SAAR of 38.9 million (compared to 3.2 million – or a SAAR of 38.8 million – in September).