August auto sales are expected to be up more than 15% vs. the same month a year ago, forecasters said.

New-vehicle sales are expected to be about 1.35 million cars and trucks in August, up about 15.4% vs. August 2022, according to a joint forecast from J.D. Power and GlobalData. In a separate forecast, S&P Global Mobility said it expects U.S. auto sales to be up about 18% in August vs. a year ago.

Positives for auto sales include better availability of new vehicles, and continued strong demand — including rental cars and commercial fleets, on top of retail demand. Meanwhile, affordability is the No. 1 worry.

According to Thomas King, president of the data and analytics division at J.D. Power, the average incentive per new vehicle in August is an estimated $1,902, roughly double what it was a year ago..

As a percentage of Manufacturer’s Suggested Retail Price, the average incentive in August was an estimated 4% of MSRP, vs. 1.9% a year ago.

To put that big increase in perspective, incentives were at a record low a year ago. Manufacturers cut incentives earlier because of low supply vs. high demand. Incentives are starting to come back as supply has come back, and demand is less red-hot. But prices today are still relatively high.

The bottom line for many consumers is that the average monthly, new-vehicle payment is an estimated $729 in August, up 2.7% vs. a year ago.

Higher interest rates are a big contributor to higher monthly payments. According to J.D. Power, the average interest rate for new-vehicle loans is expected to be 7.3% in August, vs. about 5.5% a year ago.

The average new-vehicle transaction price is down from recent all-time highs. But a very high percentage of customers are paying more than sticker price. That was rare, before the industry discovered it could raise prices amid the pandemic and new-vehicle shortages.

In August, an estimated 28.5% of new vehicles will be sold above MSRP. In August 2022, it was 46.8%, J.D. Power said.