DETROIT — U.S. auto sales were expected to drop slightly in July as unusually hot weather — and softening demand — kept buyers at home.

Kelley Blue Book predicted a 1 percent decline from last July to about 1.5 million new cars and trucks. Sales were strong at the beginning of the month thanks to Independence Day promotions, but weakened after that, KBB said.

General Motors’ sales fell 2 percent while Ford’s U.S. sales fell 3 percent. Toyota’s sales slipped 1 percent. Fiat Chrysler’s sales were flat. Volkswagen’s sales fell 8 percent.

Several automakers eked out sales increases. Hyundai’s sales were up 6 percent and Honda’s sales rose 4 percent. Nissan’s were up 1 percent.

After six straight years of growth — and record sales of 17.5 million new vehicles last year — U.S. sales are beginning to plateau. In the first six months of last year, for example, sales were up 4 percent, or more than double the pace of this year. But low gas prices, low interest rates, enticing new vehicles and strong consumer confidence should keep them at a very high level.