The National Weather Service is predicting below freezing temperatures Monday night into Tuesday morning, that could potentially be damaging to plants or exposed irrigation pipes and hoses.

Meteorologist Dan Zumpf said the cool temperatures have been coming into the Missoula valley for the last 24 hours.

"We've been getting quite a bit of cool air coming in from the east," Zumpf said. "That cold air is settling into the valleys, and with the skies clearing up and with us being in the early fall, we're getting into the period when freezing is a distinct possibility. So, tonight, all the ingredients are coming together for us to have below freezing temperatures for much of western Montana."

Zumpf said this will be the first real frost and possible hard freeze of the year, and some precautions may be necessary.

"We're going to see temperatures in the mid 20's to low 30's overnight for lows, so any sensitive plants or gardens, and even exposed irrigation pipe might need to be looked after before tonight," he said. "Some of the higher valleys have already seen below freezing temperatures, but for Missoula and the Bitterroot valleys these will be the first freezing temperatures that we've seen this year, and it's a little earlier than in years past."

Zumpf said the freezing temperatures and a warm front returning for the weekend could begin the process of leaves turning colors in western Montana signalling the beginning of Indian Summer.