Edmunds forecasts that 1,496,834 new cars and trucks will be sold in the U.S. in August for an estimated seasonally adjusted annual rate of 16.8 million. This reflects a 10.2 percent increase in sales from July 2018 and a 1.2 percent increase from August 2017. 

"Hurricane Harvey depressed August sales by 2 percent when it hit last year, which is likely why we're seeing a year-over-year lift in sales," said Jeremy Acevedo, Edmunds' manager of industry analysis. "Despite this slight boost, August sales fall in line with the slower overall sales pace we expect to see through the second half of the year."

Edmunds analysts also note that through July, inventories reached their lowest levels since 2016. While this is a positive sign that the industry has right-sized supply for decreasing demand, fewer vehicles on dealer lots means fewer vehicles are being sold compared to recent years.

"There are a lot of things working against the automotive market right now: Incentive spending is maxed out, interest rates are rising, and vehicle prices are reaching record highs," said Acevedo. "Add to that the uncertainty that comes with renegotiating NAFTA and tariff talks and it amounts to what could be a challenging back half of the year for automakers."

Edmunds estimates that retail SAAR will come in at 14.3 million vehicles in August 2018, with fleet transactions accounting for 14.5 percent of total sales. An estimated 3.4 million used vehicles will be sold in August 2018, for a SAAR of 39.7 million (compared to 3.4 million — or a SAAR of 39.5 million — in July).