Mammoth Mountain
Weather Forecast
Mammoth Mountain,Mammoth Lakes, Crowley, and Bishop.
October 9th, 2025, 3 PM – As of this update, there are mostly clear skies in the area, with just a bit of snow left from the last system that went through. However, the ground is wet and ready for the next snowfall that’s expected to arrive next Monday night and Tuesday.
Checking in on the conditions as of this post. Up Top, the temperature is 43 degrees with an SW wind at 36 mph, gusting to 53 mph. Down at Main Lodge, the wind is WSW at 5 MPH, gusting to 22 MPH, and the temperature is 55 degrees.
Recreational Weather Forecast for the Week: Expect breezy conditions to increase over the next 24 hours. Winds will be Breezy to Gusty at times over the next week. As of today, the next system is tracking too far north on Friday/Saturday to bring anything more than a few very isolated showers over the crest.
Midday temperatures at the Main Lodge are expected to range in the mid-50s into Friday, with nighttime lows in the lower 40s. By Saturday, temperatures are expected to drop into the mid-40s. Brrr, after months of warmth, it’s going to be a bit chilly. Saturday night appears to be a potential freeze at Main Lodge with lows possibly in the upper 20s.
Winds: Breezy, with a southwest wind 15 to 25 mph, with gusts as high as 45-55+ mph. Winds from this next system could peak over the crest at 70 MPH at some point.
Mammoth Lakes: Midday Temperatures are expected to be in the mid-60s through Thursday, the low 60s on Friday, and the mid-50s on Saturday. Nighttime lows in the upper 30s to lower 40s are expected on Friday night, with a deep freeze (20 Degrees) possible on late Saturday night into early Sunday morning.
For Bishop, temperatures are expected to range from the upper 70s to the lower 80s for the rest of the week, with nighttime lows in the low to mid-40s. Nighttime lows on Saturday night, for now, look to be in the mid-30s, with a possible ground frost. **I would cover sensitive plants or bring them inside.**
Winds will be breezy, with a south-southeast wind of 7 to 12 mph, increasing to 19 to 24 mph in the afternoons. Winds could gust as high as 30- 40 mph on Thursday.
Mammoth Mountain Weather Discussion
Thursday, October 9th, 2025 @ 2:30 PM
The Pacific Northwest trough dominates today, with the main 500-mb low centered well offshore of Washington and Oregon. Over California, heights are lower but stable, keeping skies mostly clear and temperatures near seasonal.
To the south, the small upper-low off Baja is the remnant energy from former Tropical Storm Priscilla, not the cutoff that impacted us earlier this week — that system has completely dissipated.
Friday – First Trough Arrival
By Friday, the trough digs farther south down the coast, with the core near 50° N / 130° W, beginning to send stronger southwest flow toward Northern California.
Winds will increase across the Sierra by late afternoon, but moisture will remain limited early in the event.
Saturday – First Wave Passage
On Saturday, the trough axis shifts inland through Northern California.
The ECMWF deterministic run keeps most QPF north of Mammoth, but shows light amounts up to 0.10–0.25″ near the crest. Expect cooler temps, breezy to windy conditions, and possibly a few flurries above 9,500–10,000 ft.
Sunday – Reinforcing Energy Drops South
By Sunday, a reinforcing shortwave digs down the West Coast, helping to deepen the larger-scale trough.
This sets the stage for a closed low to form early next week. Expect continued breezy conditions and a gradual temperature drop.
Tuesday – Potential Closed Low
By Tuesday, the ECMWF ensemble closes off a low near the Bay Area, a favorable position for southwest flow and orographic lift into the Central Sierra.
If this verifies, Mammoth could see a more substantial round of snowfall Monday night into Tuesday.
Alternate model guidance (GEFS/NBM) keeps the system more inland, which would mean a colder but drier outcome.
Snowfall – First Call (Sun–Tue Window)
Main Lodge (~9,000 ft): 3–5″
Summit / Crest (≥ 10,000 ft): 5–10″+
Confidence remains low, as is typical for transition-season systems. Expect daily refinements as the track and phasing of the early-week low become clearer. Below are 3 snowfall forecasts to check out. I’m discounting the first one as the model seems to be too wet most of the time.
Snowman’s Take
We’re moving from quiet fall weather into the first real hint of winter. The pattern evolution through Tuesday shows stronger troughs, deeper moisture taps, and colder air aloft returning to the Sierra. Whether this becomes just a teaser dusting or a meaningful early-season event will depend on that low’s final track early next week.
Steve Taylor, the Mammoth Snowman (WX Links)
Next Update Friday @ 5 PM
Images provided by WeatherBell.com
NOAA 6-10 Day & 8-14 Day Outlooks
October Seasonal Model Update – Looking Toward Winter 2025–26
10-5-25 @ 5 PM – The latest ECMWF seasonal update just dropped, and we’ve dug through every chart and model trend to see what this winter might bring to Mammoth Mountain.
The signal this year? A weak La Niña that fades fast — a setup that often means a slow start, followed by a better shot at storms once the pattern relaxes.
That’s a familiar pattern in the Eastern Sierra. Early winter can run lean while the Pacific jet stays aimed a bit north, but once it sags south, things can change in a hurry.
The key question this year isn’t whether storms will come — they will — but when the pattern opens the door and how cold those early ARs run.
Looking for years to match this Fall is tough. Here are the ones that are the closest: 2000-01 (393), 2005-06 (579), 2016-17 (618), and 2017-18 (262).
I will have more information on this in a couple of days, once I have concluded my research on past patterns.
Snowman – Next Model Update on 11/5/25
❓ 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.