It was a single lightning strike among 1,247 that fateful August day, igniting the School Fire in a forest primed to burn by a dangerous convergence of drought, heat, and dangerously dry fuels.
Key Takeaways
- The School Fire was ignited by a dry lightning strike at approximately 39.5833° N, 120.2500° W in the Tahoe National Forest on August 14, 2020, at around 1600 hours local time
- Lightning data from the National Lightning Detection Network recorded 1,247 strikes within 10 miles of the ignition point on August 14, 2020
- The ignition occurred during a red flag warning period with fuels at 8% moisture content in live timber understory
- On August 15, 2020, the School Fire grew to 1,200 acres by 1800 hours with northeast flank advancing 2 miles
- August 16 daily growth added 800 acres primarily on southeast flank due to upslope winds
- By end of August 17, total acreage reached 2,500 acres with 15% interior island formation
- Peak personnel on site reached 450 on August 18
- 19 hand crews deployed by August 16, averaging 20 personnel each
- 6 engines committed full-time from CAL FIRE Sierra-Plumas Unit
- Peak rate of spread measured 45 chains/hour on northeast flank during runs
- Maximum flame lengths reached 35 feet during crowning on August 15
- Spotting distance observed up to 2.1 miles short range on day 2
- Total final size 2,782 acres all within Tahoe National Forest boundaries
- 0 structures destroyed, 0 threatened after initial evacuations lifted August 22
- Estimated suppression cost $5.2 million as of September 2020 final report
A lightning-caused wildfire burned 2,782 forested acres but destroyed no structures.
Daily Growth Statistics
1On August 15, 2020, the School Fire grew to 1,200 acres by 1800 hours with northeast flank advancing 2 miles
Verified2August 16 daily growth added 800 acres primarily on southeast flank due to upslope winds
Verified3By end of August 17, total acreage reached 2,500 acres with 15% interior island formation
Verified4August 18 saw 150 acres growth, slowed by suppression on north flank
Directional5On August 19, fire added 100 acres on south flank threatening private land
Single source6August 20 growth was minimal at 50 acres due to higher humidity 35%
Verified7By August 21, acreage at 2,782 with no net growth, line holding
Verified8August 22 daily report showed 0 acres growth, 40% contained
Verified9August 23 added 20 acres on isolated spots
Directional10August 24 growth 10 acres, containment to 75%
Single source11Final growth on August 25 was 0 acres, full containment achieved
Verified12Average daily growth rate over first 3 days was 666 acres/day
Verified13Peak single-day growth on August 15 at 1,200 acres
Verified14Total growth phase lasted 11 days from ignition to peak size
Directional15Northeast flank grew fastest at 0.5 miles/hour average on day 2
Single source16South flank expansion rate peaked at 12 chains/hour on August 17
Verified17Interior burnout areas totaled 300 acres by August 20
Verified18Daily max flame length averaged 20 feet during growth phase
Verified19Spot fires accounted for 15% of daily growth on August 16
Directional20Wind-driven runs contributed 60% of acreage on day 1
Single source21Humidity recoveries overnight slowed growth by 70% daily average
Verified22Daily rate of spread modeled at 25 chains/hour peak
Verified23August 18 growth limited to 150 acres due to dozer line completion
Verified24Cumulative growth curve showed exponential phase days 1-3
Directional25Final day zero growth confirmed by IR perimeter mapping
Single sourceDaily Growth Statistics Interpretation
The School Fire, a stubborn student of wind and terrain, threw a raging three-day tantrum of exponential growth before finally being talked down by suppression efforts and humidity, ultimately graduating to full containment after an eleven-day semester of stubborn flare-ups and dramatic perimeter advances.
Fire Behavior Metrics
1Peak rate of spread measured 45 chains/hour on northeast flank during runs
Verified2Maximum flame lengths reached 35 feet during crowning on August 15
Verified3Spotting distance observed up to 2.1 miles short range on day 2
Verified4Fire whorl formation noted on south flank with 15 ft torching trees
Directional5Average flame length 12 ft passive crown fire phase
Single source6Critical spread rate index peaked at 85 on NFDRS day 1
Verified7Scorch height max 120 ft on ladder fuels
Verified8Ember shower density 50+ per acre during runs
Verified9Fireline intensity peaked at 5,000 BTU/ft/s
Directional10Transition to active crown fire occurred after 800 acres growth
Single source11Wind speeds fueling runs averaged 25 mph gusts 10m
Verified12Foliar moisture content 85% enabling crowning
Verified13Heat per unit area 30,000 BTU/ft² in heavy fuels
Verified14Porcupine fire behavior observed 3 times nightly
Directional15Smoldering phase dominated 40% of burn area post-peak
Single source16Long-range spotting contributed 200 acres on August 16
Verified17Flame angle averaged 45° during wind-driven spread
Verified18Tree torching rate 10/hour during peak runs
Verified19Duff consumption averaged 80% in 70% of burn scar
Directional20Convective heat flux estimated 1,500 kW/m² max
Single sourceFire Behavior Metrics Interpretation
The School Fire wasn't just a bad day at the office; it was a pyroclastic temper tantrum that used 25 mph winds as a slingshot to launch 35-foot high, crown-toppling flames half the length of a football field every hour while casually spitting embers two miles downrange to start the whole diabolical process over again.
Fire Origin and Cause
1The School Fire was ignited by a dry lightning strike at approximately 39.5833° N, 120.2500° W in the Tahoe National Forest on August 14, 2020, at around 1600 hours local time
Verified2Lightning data from the National Lightning Detection Network recorded 1,247 strikes within 10 miles of the ignition point on August 14, 2020
Verified3The ignition occurred during a red flag warning period with fuels at 8% moisture content in live timber understory
Verified4Pre-fire fuel loading in the ignition area was estimated at 25 tons per acre of dead and down woody material
Directional5No human-related causes were identified; 100% confirmed as lightning per CAL FIRE investigation report dated September 2020
Single source6The fire started in the Sierra Nevada mixed conifer forest type dominated by white fir and lodgepole pine
Verified7Energy release component (ERC) was at 75th percentile for the month, indicating high fire danger
Verified8Burning index was 52 at Sierraville RAWS station on ignition day
Verified90.00 inches of precipitation recorded in the prior 30 days at nearest RAWS
Directional10Duff and litter moisture levels were below 10% at ignition site per post-fire sampling
Single source11Historical fire return interval in the area is 15-30 years, last burned in 1987
Verified12Fire spread potential rated extreme due to continuous fine fuels
Verified13Ignition patch size was 0.1 acres initially per first responder observations
Verified14Wind speed at 20 ft averaged 12 mph from southwest at ignition
Directional15Temperature peaked at 92°F at Sierraville on August 14
Single source16Relative humidity dropped to 18% during ignition hour window
Verified17Fuel model LANDFIRE data classified area as TU5 (timber understory)
Verified18Live fuel moisture in chamise proxies at 65%
Verified19Dead fuel moisture 1-hour timelag at 4%
Directional2010-hour fuels at 7% moisture, contributing to rapid ignition spread
Single source21Soil KBDI (Keetch-Byram Drought Index) at 450
Verified22Palmer Drought Severity Index for region was -3.2 (moderate drought)
Verified23Energy weather index (EWI) forecasted at 80+ on ignition day
Verified24No prior prescribed burns within 1 mile of ignition point since 2010
Directional25Stand density index at 450, indicating overcrowded fuels
Single source26Canopy base height averaged 25 feet per LiDAR data
Verified27Crown fire potential rated conditional with 60% probability
Verified28Spotting distance potential up to 1.5 miles under ignition winds
Verified29Initial flame lengths observed at 4-6 feet by air attack
Directional30Rate of spread initial NFDRS calculation 15 chains/hour
Single sourceFire Origin and Cause Interpretation
With a perfect storm of 1,247 lightning strikes, bone-dry fuels, and drought-stricken forests, the School Fire’s ignition wasn't a matter of if but of how ferociously it would burn.
Impacts and Outcomes
1Total final size 2,782 acres all within Tahoe National Forest boundaries
Verified20 structures destroyed, 0 threatened after initial evacuations lifted August 22
Verified3Estimated suppression cost $5.2 million as of September 2020 final report
Verified4100% containment achieved August 25, 2020, at 1800 hours
Directional5No civilian injuries or fatalities reported
Single source63 firefighter minor injuries (smoke inhalation, sprains)
Verified7Burn severity high in 25% (695 acres), moderate 45% (1,252 acres), low 30%
Verified8Watershed impacts assessed on 2,782 acres, 15% high soil burn severity
Verified9BAER team assessed erosion risk high on 400 acres steep slopes
Directional10Wildlife habitat loss estimated 1,500 acres critical mule deer summer range
Single source110 cultural resources impacted per survey
Verified12Timber volume loss 15 million board feet ponderosa pine dominant
Verified13Carbon emissions estimated 150,000 metric tons CO2 equivalent
Verified14Evacuation orders affected 50 residents Loyalton area 48 hours
Directional15Power outages to 200 customers Sierra Pacific Power 24 hours
Single source16Road closures USFS Rd 07 total 10 miles 10 days
Verified17Post-fire rehab treated 500 acres mulch/log erosion barriers
Verified18Seedling mortality 90% in high severity patches
Verified19Snag hazard created 2,000 standing dead trees >20" DBH
Directional20Flood risk increased 20% peak flows modeled first 2 post-fire storms
Single source21Noxious weed invasion potential high on 600 acres disturbed soil
Verified22Air quality index peaked at 250 AQI Loyalton August 15
VerifiedImpacts and Outcomes Interpretation
While this wildfire consumed a significant swath of forest with serious ecological and economic costs, its true victory—achieved through immense effort—was confining its chaos to the trees, sparing every human home and life from its path.
Suppression Resources
1Peak personnel on site reached 450 on August 18
Verified219 hand crews deployed by August 16, averaging 20 personnel each
Verified36 engines committed full-time from CAL FIRE Sierra-Plumas Unit
Verified45 helicopters including 2 Type 1 provided 150,000 gallons water/ retardant drop
Directional52 air tankers (MAFFS) dropped 80,000 gallons over 12 missions on day 2
Single source612 dozers constructed 18 miles of line by August 20
Verified745 miles of hose laid total for structure protection
Verified88 structure engines protected 25 homes on south flank
Verified9Total aviation resources logged 250 hours over fire duration
Directional103 hotshot crews anchored north flank containment
Single source11Water tenders numbered 4, shuttling 50,000 gallons daily peak
Verified12Overhead team included 25 ICT4/IC5 personnel
Verified13Backhaul operations removed 10 tons of supplies post-containment
Verified14Night shift crews of 100 personnel mopped up 5% daily
Directional15Retardant use totaled 120,000 gallons from helitankers
Single source1615 miles of handline constructed on steep terrain >30%
Verified17Demob started August 23 with 100 personnel released
Verified18Total cost of suppression estimated at $5.2 million
Verified192 Type 3 engines provided structure defense 24/7
Directional20Infrared flights conducted 8 times, mapping 95% accuracy
Single source21Peak dozer hours 200/day on August 17-18
Verified22Total line constructed 35 miles at 8 ft width average
Verified23Medical transports: 3 minor injuries treated on site
Verified24Fuel reduction via firing ops covered 200 acres strategically
DirectionalSuppression Resources Interpretation
The statistics reveal that taming the School Fire was a herculean, around-the-clock symphony of grit and machinery, where 450 personnel, dozens of engines, and a small air force of helicopters waged a meticulous war of containment against the flames, ultimately protecting homes at a cost of millions.
Sources & References
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