With Starbucks’ pumpkin-spice lattes in hand, natural gas traders sent forward prices plummeting as crisp air began moving into the country even as Texas continued to bake under triple-digit temperatures. October forward prices fell by an average 30.0 cents from Aug. 31-Sept. 6, with West Coast markets leading the way as losses there were more than double that amount, according to NGI’s Forward Look.

The sharp sell-off extended through the upcoming winter (November-March) as prices dropped an average 24.0 cents through the period, Forward Look showed. Prices for next summer (April-October) were down only 9.0 cents on average, however.

For most U.S. markets outside of the West, the price swings lower across the forward curve came as weather models showed more moderate...