Mammoth Mountain Weather & Discussion
Almost Daily Weather for Mammoth Mountain and the Southern Eastern Sierra
Monday, September 21st, 2026 @ 6:00 AM – Expect increasing clouds as an open low is expected to move right over the region from about Mt Whittny to just north of Mammoth Mountain.
This low will bring a 50% chance of showers today, with snow levels around 10,500 feet this morning, rising to about 11,200 feet by the afternoon.
If the mountain gets under a heavy shower, that could briefly pull snow levels down a bit. The ground is still warm, so any snow that does fall is unlikely to accumulate.
Mammoth Weather Forecast: Main Lodge / Mammoth Lakes Basin… A 50 percent chance of showers after 11 am. Widespread haze before 10 am. Partly sunny, with a high near 56. North wind around 5 mph becoming southwest in the afternoon. Winds could gust as high as 20 mph.
Mammoth Lakes… A 50 percent chance of showers after 11 am. Widespread haze before 10 am. Partly sunny, with a high near 61. Calm wind becoming east around 5 mph in the afternoon. Winds could gust as high as 20 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
Models are in what we call transition season… aka don’t trust anything beyond 7-10 days.
Below is the 10 Day run from the EPS Mean. I have also posted the snowfall and QPF images for today.
500mb Height & Anomaly
Today’s QPF from the ECMWF
Today’s snowfall model data from the ECMWF
Today’s snowfall model data from the RFFF, the replacement for the HRRR model.
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.