Weekly natural gas cash prices posted a modest late-summer gain as heat festered in key regions, driving enough cooling demand to support the national average to kick off September.

NGI’s Weekly Spot Gas National Avg. for the holiday-shortened Sept. 5-8 trading period rose 6.5 cents to $2.355.

While forecasts pointed to an easing of the heatwaves that dominated August and the beginning of the current month, pressuring futures markets, summer weather held through the latest week in the South and West. This kept air conditioners cranking and supported spot prices.

SoCal Citygate finished the four-day week up 58.5 cents to $3.505, while Northwest Sumas gained 29.5 cents to $2.365.

In the Southwest, El Paso S. Mainline/N. Baja advanced 22.0 cents to $2.780.

The October...