Edmunds is forecasting 1,392,434 new vehicles sales through September, representing a 5.4% decline from March and an 8.3% decline from the same time last year.

Of those 1.3 million new vehicles sold, roughly 15.2% are expected to originate from fleet sales, according to a release from Edmunds.

Meanwhile, in the used segment, 3.3 million vehicles are expected to sell, a decline from the 3.4 million sold in August.

"Vehicle replacement demand following Hurricane Harvey bolstered auto sales last September, and Hurricane Florence has had a very limited impact on auto sales this month, which are the primary reasons why we're seeing this year-over-year decline," said Jeremy Acevedo, Edmunds' manager of industry analysis. "With that said, a SAAR of 17 million is certainly not an unhealthy number — September is still shaping up to be a robust month for sales."

In terms of market share, GM, Ford, and Nissan are the only three OEMs expected to see a decline, on a year-over-year basis.