Western States 100 Weather Guide: Complete Preparation for the California Canyons

The Western States Endurance Run, held each June from Squaw Valley to Auburn, California, is often called the world's oldest 100-mile trail race. It's also one of the most demanding in terms of weather, asking runners to manage a full spectrum of conditions across its 100-mile course: from potential snow and freezing temperatures at the high-altitude start above 8,000 feet, to brutal heat exceeding 100°F in the canyons during the late afternoon. No other major ultramarathon packs such extreme weather variation into a single race. Understanding Western States weather—the patterns, the risks, the preparation required, and the cooling strategies that can save your race—is essential knowledge for anyone fortunate enough to earn a spot on the start line.

This guide covers everything about Western States weather: the course's weather profile from start to finish, historical conditions and what to expect, training for extreme heat, race-day strategies for managing both cold and heat, and what makes this race's weather challenge unique in ultrarunning.

The Western States Weather Profile

Understanding the Course Geography

How terrain creates weather:

The starting point:

Olympic Valley (formerly Squaw Valley)
Elevation: ~6,200 feet at start
Quickly climbs to Emigrant Pass: 8,750 feet
High Sierra Nevada mountains
Weather is mountain weather

The canyons:

After the high country, course descends into river canyons
Elevation: 1,000-3,000 feet in low sections
American River watershed
Heat builds and lingers in these confined valleys
This is where the suffering happens

The finish:

Auburn, California
Elevation: ~1,350 feet
Foothills of Sierra Nevada
Hot in afternoon, moderating overnight
Last section can still be quite warm

The overall profile:

18,000+ feet of climb
23,000+ feet of descent
Temperature can vary 50°F from start to canyon floor
Multiple microclimates
Weather changes constantly

The Race Day Weather Pattern

What typically unfolds:

Morning high country (first 6-8 hours):

Start temperature: 30-50°F typical
Can be colder with wind
Snow possible on high ridges
Clear or partly cloudy typical
Runners in long sleeves, sometimes jackets

Midday transition (hours 8-14):

Descending toward canyons
Temperature rises steadily
By Michigan Bluff (~55 miles): 80-90°F common
Sun exposure increases on exposed ridges
Layers come off; cooling becomes focus

Afternoon canyons (hours 14-20):

The infamous heat
Canyon temperatures: 95-105°F+
Direct sun plus radiated heat from rock
American River crossings provide relief
This is the crucible

Evening and overnight (hours 20+):

Temperature slowly drops
But may stay 70-80°F in canyons
Cooling accelerates after 9 PM
Front-runners in relative cool
Back-of-pack runners get extended heat exposure

The Heat Challenge

Why Western States Heat Is Different

What makes it legendary:

Duration of exposure:

Unlike short races where heat is temporary
Western States runners face 10-15+ hours of significant heat
For back-of-pack runners: Potentially 20+ hours
Cumulative heat stress is the issue
Body's ability to cope degrades over time

Canyon thermal dynamics:

Heat settles into canyons
Rock walls absorb and radiate heat
Air doesn't circulate well
Temperature can be 10-15°F hotter than ridges
You're running through an oven

Historical numbers:

Canyon temperatures above 100°F are routine
Some years have seen 105-110°F
Cooler years (90s) are gifts
Heat is the expected condition
Prepare for worst, hope for best

The timing trap:

Fastest runners clear canyons before peak heat
Mid-pack hits canyons at worst time (2-6 PM)
Back-of-pack runners in heat even longer
Slower runners face more heat
Speed advantage compounds

Heat Effects on Performance

What happens to your body:

Cardiovascular strain:

Heart works harder to cool you
Blood diverts to skin for heat dissipation
Less blood available for muscles
Heart rate skyrockets at normal pace
What felt easy in morning feels brutal in heat

Dehydration cascade:

Sweat rates can exceed 2 liters/hour
Impossible to replace all fluid
Progressive dehydration is inevitable
Gut absorption decreases with heat
Drinking more doesn't solve it

GI distress:

Heat diverts blood from gut
Absorption slows
Nausea common
Vomiting ends many races
Nutrition strategy must account for heat

Cognitive effects:

Confusion, disorientation possible
Decision-making degrades
May not recognize you're in trouble
Crew and aid station help is critical
The danger is real

Training for Western States Heat

Preparing your body:

Heat acclimatization protocol:

Begin 10-14 days before race (minimum)
60-90 minutes of heat exposure daily
Running in heat is most effective
Sauna post-run as supplement
Must maintain through race day

What acclimatization provides:

Increased sweat rate and efficiency
Expanded blood plasma volume
Lower core temperature at given effort
Earlier sweating (begins sooner)
10-20% performance improvement possible

Training in heat:

If you live in cool climate, seek heat
Travel to hot locations for training
Overdress in cooler conditions
Use heat chamber if available
Don't show up untrained for heat

Sauna protocols:

Post-exercise sauna (15-30 minutes)
4-7 sessions per week during acclimatization period
Temperature: 180°F or higher
Hydrate before and after
Research-supported method

The Cold Challenge

High Country Conditions

The other extreme:

Typical high-country weather:

Overnight low at Squaw: 30-45°F
Emigrant Pass summit: Often 30s
Wind chill can drop significantly
Snow possible on ground or falling
Remember: Race starts at 5 AM

Cold-related risks:

Hypothermia possible if conditions worsen
Runners start cold and take time to warm up
Sweating in early climbs + wind later = chill risk
Mandatory gear exists for a reason
The high country demands respect

Historical extremes:

Some years have seen significant snow
Cold rain has affected races
Front runners move through quickly
Slower runners may spend 6+ hours in mountains
Cold exposure time matters

Managing the Cold Start

Race-day strategy:

Clothing for start:

Layers that can be removed
Arm warmers highly useful
Light shell for wind/weather
Gloves and hat if cold
Don't overdress (you'll warm up)

The warming process:

First major climb (to Emigrant Pass) generates heat
By Watson's Bar (35 miles), transitioning to heat
Layers come off gradually
Drop crew can take excess clothing
Plan what you'll wear and when

Drop bag strategy:

Forest Hill (62 miles): Have both cold and heat gear available
By Forest Hill, know what conditions actually are
May need different gear than expected
Flexibility in drop bags is key
Plan for multiple scenarios

Race Day Cooling Strategies

Active Cooling Techniques

Managing body temperature:

Ice everywhere:

Under hat/bandana
In sports bra (women) or shirt
Carry in hands
Down shorts
Every ice point is valuable

Water dousing:

Water over head repeatedly
Soak shirt
Bandana wet around neck
Arms and legs
Any exposed skin

Creek crossings:

Western States has natural cooling points
American River crossings are cherished
Full immersion when possible
Don't rush through—linger
Some runners call creeks "the best aid stations"

Pre-cooling:

Ice vest at crew points
Cold towels
Drink cold fluids
Shade whenever available
Proactively cool, don't just react

Aid Station and Crew Strategy

Using support:

Aid station protocol:

Don't rush through in heat
Take time to cool
Ice, water, shade
Brief stop is worth it
Frantic rushing increases core temp

Crew focus:

Crew's job in canyons: Keep you cool
Have ice and cold water ready
Cold towels prepared
Shade if possible
Runner may not be thinking clearly—crew leads

Pacing through heat:

Consider hiking in hottest sections
Running generates more heat
Walking still moves you forward
Many successful finishers walk the canyons
Pace discipline saves races

Historical Perspective

Weather Patterns Through Years

What history shows:

The hot years:

Canyon temperatures exceeding 105°F
Higher DNF rates
Medical issues spike
Even prepared runners struggle
These years test everyone

The moderate years:

Canyons in 90s
Challenging but manageable
Still requires preparation
Not a "gift"—still hard
Performance benefits from less extreme heat

The unusual years:

Snow and cold have affected some years
Rain and mud occasionally
Weather systems can bring surprises
Flexibility required
Race what you get

The trend:

Climate change may be increasing heat events
Historically hot years becoming more common
The challenge isn't diminishing
If anything, heat preparation more critical than ever
Don't count on a "cool year"

Learning from Western States DNFs

What goes wrong:

Heat-related DNFs:

Many runners underestimate heat
Acclimatization often insufficient
Pacing too aggressive in canyons
Not enough ice and cooling
Running when walking is smarter

The common pattern:

Feel good in morning (cool)
Push pace while conditions allow
Enter canyons in heat
Core temp rises, can't bring it down
GI failure, confusion, medical pull
The race ends in Foresthill or canyons

What finishers do differently:

Extensive heat training
Conservative early pacing
Aggressive cooling strategy
Accept walking in heat
Prioritize finishing over time

Final Preparation

The Weeks Before

Getting ready:

2-3 weeks out:

Heat acclimatization must be underway
Sauna sessions after runs
Hot runs if possible
Building heat tolerance
Don't start too late

Race week:

Maintain heat exposure
Don't lose acclimatization to taper
Continue short sauna sessions
Monitor weather forecast
Adjust expectations to actual forecast

Pre-race:

Know where ice/cooling is on course
Brief crew on cooling strategy
Pack ice in drop bags (if allowed)
Have multiple cooling options
Be prepared for the heat you'll face

Race Morning Mindset

Mental preparation:

Accept the challenge:

Western States is supposed to be hard
The heat is part of the experience
Every finisher has managed this weather
You've prepared for this
Embrace rather than fear

Commit to the strategy:

When heat hits, follow your plan
Walk if you planned to walk
Cool aggressively as planned
Don't abandon strategy because you feel "fine"
The plan is there for when you don't feel fine

Respect the race:

100 miles with this weather variety is unique
The weather is what makes Western States Western States
Finishing is the accomplishment
Time is secondary to completion
The belt buckle recognizes the achievement

Key Takeaways

Temperature can vary 50°F+ across the course. From potential freezing at the start to 100°F+ in the canyons.
Heat acclimatization is mandatory. 10-14 days minimum of daily heat exposure; without it, you'll suffer.
Canyon heat is the race's defining challenge. Expect temperatures above 100°F in the canyons during afternoon hours.
Aggressive cooling isn't optional. Ice everywhere, water dousing, creek immersion—use every opportunity.
Pace discipline in heat saves races. Walking the canyons is often the right strategy; running generates more heat.
Slower runners face more heat. The mid-pack hits canyons at peak heat; back-of-pack runners face extended exposure.
Sauna protocols are research-supported. Post-exercise sauna sessions accelerate heat adaptation.
Finishing is the accomplishment. Managing Western States weather is what earns the belt buckle.

Western States 100 is the ultimate weather challenge in ultrarunning—from mountain snow to canyon furnace in a single race. Run Window can help you train in varied conditions, but preparing for Western States requires deliberate, extensive heat adaptation.