Snow has dusted the mountain peaks of the West in several states this week in the final days of summer. The official start of fall is Wednesday, Sept. 23.

in California's Sierra Nevada said that Monday's dusting was the first of the season there. Farther north in the Sierra, said they received their first flakes of the season Wednesday.

Sierra Nevada ski resorts in California are hoping that El Nino will help boost snowpack this winter season. The snowpack last winter in the Sierra was the lowest in 500 years,

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and also indicated that this week's snow was the first of the season. Photos provided to weather.com by Jeremy Swansonfrom Aspen Snowmass show a brilliant contrast between vivid fall foliage and snow dusting the peaks in the area.

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September Snow in the West

Aspen Snowmass in Colorado on Sept. 15, 2015. (Credit: Jeremy Swanson)

Other areas that have seen snow in the West this week include, which saw a dusting of snow Wednesday, and the Crater Lake area of southern Oregon. The National Weather Service in Portland, Oregon, said that

Snow is not unusual in the higher elevations of the West during September. In fact, .

The snow this week in the West is the result of a pattern change that took place, with a jet stream dip moving south over the region, allowing cooler temperatures to take hold. Embedded in that jet stream dip are disturbances aloft that have just enough moisture to work with to produce snow in the higher elevations and rain in the valleys.

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