Mammoth Mountain Weather & Discussion
Almost Daily Weather for Mammoth Mountain and the Southern Eastern Sierra
Monday, October 5th, 2026 @ 10 AM – Clear skies over Mammoth Mountain and the Eastern Sierra today. At the Summit, the temperature is 46 degrees with a N wind at 6 to 15 MPH. Main Lodge is 60 with a light east wind. Yesterday’s high temp at 9,000 feet was 68 degrees.
Summary: Warmer days continue under a ridge of high presure that will be in the area throughout the week. If you like cooler weather, things will change by Sunday. Both the EPS and GEFS ensembles have a fairly deep but dry trough in the area by Sunday. Read about the details below in the full discussion.
Mammoth Weather Forecast: Main Lodge / Mammoth Lakes Basin: Today into Friday, Sunny, with highs in the upper 60s. Calm wind becoming southwest around 5 mph in the afternoon.
Mammoth Lakes: Today into Friday, Sunny, with a high near 72. Calm wind becoming northeast 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
October 5th, 2026 @ 10 AM – Another week of ridging, and then a trough will drop into the Eastern Sierra, bringing much cooler air and windy conditions.
The low’s current path is dry; however, if it ends up a bit farther west, there could be some moisture to work with, resulting in a dusting of snow.
We’ll continue to watch the low’s track and report back Wednesday on what the ensemble paths show. Hopefully the pattern shifts west.
The ultra-long-range EPS weekly model trends continue to show a shift to a zonal flow with about-average heights after October 21st. Both the EPS and GEFS show some moisture working its way in at times late in the Month and into November.
However, if you recall last season, ensembles also showed early snowfall and lower heights that each model run pushed back well into December.
I’m encouraged to see the ECMWF Seasonal and the CFS now have a weak to moderate wet signal for November. I’ve never been a big fan of the CFS, but it’s been green almost daily in the runs for November.
That lines up with other strong eastern-based El Niño Novembers from the past. Those seasons saw 2-4 feet fall around Main Lodge during November before Thanksgiving. See image down the page…
Snowman
Below is the 16 Day run from the EPS Mean 500mb Height & Anomaly
Today’s Temperature Anomaly data from the ECMWF – Yep, red means warm days and nights. And the blue is the cooler temps as the low drops in over the weekend.
Today’s QPF from the ECMWF – Just about Nada
ECMWF Seasonal & the CFS now have a weak to moderate wet signal for November. Sure beats the brown I have seen the last several years; let’s hope something verifies and we get a bunch of base snow. Both models have wet signals for December and Janaury as well.
Mammoth Weather Discussion & Fantasy Long-Range Outlook
September 29, 2026, 10 AM – It’s game on for our ultra-fantasy long-range watch. The next 45 days will tell us whether opening day is the WROD or whether we have 10-plus runs to choose from. That will depend on both natural snow and nights cold enough for snowmaking.
I use the ECMWF Weeklies to look for long-range weather trends, not to forecast snowfall weeks in advance at Mammoth. Right now, the Weeklies trend toward ridging for the first two to three weeks of October. If that holds, we’re looking at some gorgeous fall weather for the Fall color show and all the other high-country activities you love.
The Weeklies now extend to within two days of the opener. What catches my eye farther out is a possible pattern change around October 21/25th: lower heights, a more zonal flow, and some possible moisture late month and into early November.
Another wild card after mid-month is a typhoon sending energy downstream. We saw a strong typhoon send energy into the pattern to our north just last week. If something similar lines up out three or four weeks from now, it could help open the door to an early-season storm. That’s something to watch, not a storm call.
>>> Past strong east-based El Niño Falls have brought some decent early base snow and snowmaking windows with the mountain open by November 10.
Below is the 16 Day run from the EPS Mean 500mb Height & Anomaly
Today’s Temperature Anomaly data from the ECMWF
Today’s QPF from the ECMWF
Long Range Ultra Fanatsy EPS Weeklies Mean 500mb Height & Anomaly 
30 Day Snowfall Trend into November 12 on the ECMWF Weeklies – THIS IS NOT A FORECAST – DO NOT REPOST THIS IMAGE
The last 12 CFS Weeklies show some early November wet signs. lol yes I know it’s the CFS, but I’m just showing you all what I’m looking at and hoping it’s a sign of an early start to natural snowfall. I’m a dreamer… bring it on lol.
The newest ECMWF Seasonal Model came out on September 5; 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.
❓ 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.