With no chance for significant rain or snow in the near-term forecast, western Boulder County will begin fall today under a fire ban.

As temperatures continue to hover in the 80s, Sheriff Joe Pelle enacted a fire ban Tuesday for the mountain regions of western Boulder County.

The ban remains in effect until the sheriff decides otherwise. It covers all unincorporated areas west of Colo. 93, Broadway and U.S. 36, including Rabbit Mountain Open Space and the area west of Rabbit Mountain Open Space to U.S. 36.

A very wet spring led to strong growth among grasses and shrubs in the mountains west of Boulder. With the hot, dry and, at times, windy weather expected for the rest of September, those plants easily could ignite, Pelle said.

“We’ve grown a lot of fuel this summer,” he said. “We had a very wet spring and early summer, so the grasses and shrubs and stuff are deep and lush. Well they’ve now cured and dried and they’re pretty volatile.

“So we are trying to limit the potential for ignition by limiting the kind of backcountry fires that aren’t monitored or regulated by anybody.”

The ban prohibits slash fires, fireworks or model rockets, all outdoor spark- or flame-producing activities and most outdoor burning.

Allowable activities include indoor fires in fireplaces or stoves, smoking indoors or in a vehicle, campfires in maintained campgrounds as long as the fuel is smaller than 2 feet in diameter and shorter than 3 feet tall, liquid- or gas-fuel stoves, charcoal grills on private lands, smoking outdoors in areas without flammable materials and fires contained in fire pits or grates on private land.

Those found in violation of the ban may face a $500 fine.

Pelle said “every weekend” people camp in the backcountry in Boulder County and inadvertently leave hot embers on the ground, which can be blown around by wind.

The ban comes as the National Weather Service calls for higher-than-average temperatures next week and into early October.

The average high temperature for the end of September is around 75, said meteorologist Scott Entrekin, and next week’s forecast calls for highs in the mid-to-upper 80s, with little chance for rain.

“Essentially it’s looking fairly dry here through even the first few days of October,” Entrekin said.

Boulder nearly topped the temperature record set in 2007 on Monday with a high of 88, one degree short of the historic mark, Entrekin said.

Though there was a slight chance for thunderstorms and showers overnight, Pelle said it likely wouldn’t be enough to douse the grasses, shrubs and logs on the ground in the mountains.

“We need sorta soaking rains in order to saturate the fuels and we don’t see that in the future,” he said.

Sarah Kuta: 303-473-1106, kutas@dailycamera.com or twitter.com/sarahkuta