Mammoth Mountain Weather & Discussion
Almost Daily Weather for Mammoth Mountain and the Southern Eastern Sierra
Friday, September 18th, 2026 @ 1 PM – A nice early Fall day in the Eastern Sierra. Expect mostly clear skies, dry weather, and just below-average temps into next week. The EU model does show a slight chance of showers early next week, but it would be very isolated at best; snow levels would be above 12,500 to 13,000 feet.
3 Day Weather Forecast: Main Lodge / Mammoth Lakes Basin… Saturday – Patchy smoke after 4 pm. Sunny, with a high near 65. North wind around 5 mph becoming southwest in the afternoon. Sunday – Mostly sunny, with a high near 63. Calm wind becoming south around 5 mph in the afternoon.
Mammoth Lakes… Saturday – Patchy smoke after 5 pm. Sunny, with a high near 72. Calm wind becoming west around 5 mph in the afternoon. Mostly sunny, with a high near 70. Calm wind becoming southeast around 5 mph.
Fire Permits and Restrictions: Stage 1 Fire Restrictions are in place. To learn more about the USFS Fire Restrictions, visit this link.
North East Pacific Infrared Satellite Image
Mammoth Weather Discussion & Fantasy Long-Range Outlook
Friday, September 18th, 2026 @ 1 PM – Models are in what we call transition season. Not much trust in anything beyond 7 -10 days. If you look at the MSLP posted above, you can see a typhoon in the western Pacific and how it merges with the jet stream and sends rain and snow into the Whistler area in about a week.
If we see something like this a month out, it could bring energy toward Mammoth. We have seen early openers from that type of event in the past; while rare, I watch for it each early fall season.
As of now, I don’t see any first-dusting setups; it’s been a bunch of years since that happened around the 3rd week of September, so it doesn’t look likely for Mammoth Mountain this year.
Some of the higher peaks to our south above Bishop and Rock Creek Canyon might see a flake or two next week above 13,000 feet.
Have a great day. Snowman out:)
500mb Height & Anomaly
Snowfall Model Data from the EPS Mean, with some high-elevation snow to the north and south of Mammoth.
The newest ECMWF Seasonal Model came out on September 5th; here is your Winter Precipitation Outlook from November into March. While this model has a drier November, the less-trustworthy CFS shows a wetter November.
Weather Videos
❓ Top Mammoth Weather Questions (from the Snowman)
When does Mammoth usually get its first snowfall?
Light snow can fall in late September, but consistent snowfall usually begins in late October or early November. Opening Day typically lands between November 10 and Thanksgiving, depending on storm activity and snowmaking.
How does the ENSO pattern affect Mammoth’s late fall and winter weather?
ENSO (El Niño/La Niña) plays a big role in Sierra storm patterns. El Niño winters often bring warmer, wetter storms. La Niña typically favors colder, backloaded seasons with more snow from February through April. Neutral years are the wildcards with high variability.
What is 500mb height and why does it matter?
500mb height maps show atmospheric pressure around 18,000 feet — a critical layer for tracking storm tracks, ridging, and jet stream placement. Watching 500mb patterns helps forecast Mammoth’s incoming storms and long-range trends.
What are the PNA and PDO, and how do they affect Mammoth weather?
The PNA (Pacific-North American Pattern) influences western U.S. ridging and troughing. A negative PNA favors cold, stormy setups. The PDO (Pacific Decadal Oscillation) affects sea surface temperatures in the North Pacific — a negative PDO often aligns with enhanced storm delivery into California during winter.
👉 Want more answers? Check out the full Mammoth Weather FAQ – 50 Expert Answers to learn more about storms, snow, winds, and long-range patterns from a trusted local source.
Author Bio: Steve Taylor, The Mammoth Snowman. Over the last 40+ years, Steve has spent countless hours studying and learning about Mammoth Mountain Weather and Snow Conditions.
Dr. George, Don Marcelin, Howard Sheckter, and Ted Schlaepfer were his weather mentors at that time. Steve used to hang out with Howard in the Weather War room in the early ’90s, getting first-hand knowledge of Mammoth Weather from the (The Dweeb) himself.
Steve has spent countless hours reading, studying, and watching weather discussions from the NWS and multiple Private Weather Forecasters. He is a long-time member of WeatherBell, Weather West, and AccuWeather Pro. Disclaimer: Steve is a hobbyist forecaster with over 35 years of experience reporting recreational weather and travel reports for the Mammoth Lakes area.