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
- 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
- August 18 saw 150 acres growth, slowed by suppression on north flank
- On August 19, fire added 100 acres on south flank threatening private land
- August 20 growth was minimal at 50 acres due to higher humidity 35%
- By August 21, acreage at 2,782 with no net growth, line holding
- August 22 daily report showed 0 acres growth, 40% contained
- August 23 added 20 acres on isolated spots
- August 24 growth 10 acres, containment to 75%
- Final growth on August 25 was 0 acres, full containment achieved
- Average daily growth rate over first 3 days was 666 acres/day
- Peak single-day growth on August 15 at 1,200 acres
- Total growth phase lasted 11 days from ignition to peak size
- Northeast flank grew fastest at 0.5 miles/hour average on day 2
- South flank expansion rate peaked at 12 chains/hour on August 17
- Interior burnout areas totaled 300 acres by August 20
- Daily max flame length averaged 20 feet during growth phase
- Spot fires accounted for 15% of daily growth on August 16
- Wind-driven runs contributed 60% of acreage on day 1
- Humidity recoveries overnight slowed growth by 70% daily average
- Daily rate of spread modeled at 25 chains/hour peak
- August 18 growth limited to 150 acres due to dozer line completion
- Cumulative growth curve showed exponential phase days 1-3
- Final day zero growth confirmed by IR perimeter mapping
Daily 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
- 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
- Fire whorl formation noted on south flank with 15 ft torching trees
- Average flame length 12 ft passive crown fire phase
- Critical spread rate index peaked at 85 on NFDRS day 1
- Scorch height max 120 ft on ladder fuels
- Ember shower density 50+ per acre during runs
- Fireline intensity peaked at 5,000 BTU/ft/s
- Transition to active crown fire occurred after 800 acres growth
- Wind speeds fueling runs averaged 25 mph gusts 10m
- Foliar moisture content 85% enabling crowning
- Heat per unit area 30,000 BTU/ft² in heavy fuels
- Porcupine fire behavior observed 3 times nightly
- Smoldering phase dominated 40% of burn area post-peak
- Long-range spotting contributed 200 acres on August 16
- Flame angle averaged 45° during wind-driven spread
- Tree torching rate 10/hour during peak runs
- Duff consumption averaged 80% in 70% of burn scar
- Convective heat flux estimated 1,500 kW/m² max
Fire 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
- 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
- Pre-fire fuel loading in the ignition area was estimated at 25 tons per acre of dead and down woody material
- No human-related causes were identified; 100% confirmed as lightning per CAL FIRE investigation report dated September 2020
- The fire started in the Sierra Nevada mixed conifer forest type dominated by white fir and lodgepole pine
- Energy release component (ERC) was at 75th percentile for the month, indicating high fire danger
- Burning index was 52 at Sierraville RAWS station on ignition day
- 0.00 inches of precipitation recorded in the prior 30 days at nearest RAWS
- Duff and litter moisture levels were below 10% at ignition site per post-fire sampling
- Historical fire return interval in the area is 15-30 years, last burned in 1987
- Fire spread potential rated extreme due to continuous fine fuels
- Ignition patch size was 0.1 acres initially per first responder observations
- Wind speed at 20 ft averaged 12 mph from southwest at ignition
- Temperature peaked at 92°F at Sierraville on August 14
- Relative humidity dropped to 18% during ignition hour window
- Fuel model LANDFIRE data classified area as TU5 (timber understory)
- Live fuel moisture in chamise proxies at 65%
- Dead fuel moisture 1-hour timelag at 4%
- 10-hour fuels at 7% moisture, contributing to rapid ignition spread
- Soil KBDI (Keetch-Byram Drought Index) at 450
- Palmer Drought Severity Index for region was -3.2 (moderate drought)
- Energy weather index (EWI) forecasted at 80+ on ignition day
- No prior prescribed burns within 1 mile of ignition point since 2010
- Stand density index at 450, indicating overcrowded fuels
- Canopy base height averaged 25 feet per LiDAR data
- Crown fire potential rated conditional with 60% probability
- Spotting distance potential up to 1.5 miles under ignition winds
- Initial flame lengths observed at 4-6 feet by air attack
- Rate of spread initial NFDRS calculation 15 chains/hour
Fire 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
- 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
- 100% containment achieved August 25, 2020, at 1800 hours
- No civilian injuries or fatalities reported
- 3 firefighter minor injuries (smoke inhalation, sprains)
- Burn severity high in 25% (695 acres), moderate 45% (1,252 acres), low 30%
- Watershed impacts assessed on 2,782 acres, 15% high soil burn severity
- BAER team assessed erosion risk high on 400 acres steep slopes
- Wildlife habitat loss estimated 1,500 acres critical mule deer summer range
- 0 cultural resources impacted per survey
- Timber volume loss 15 million board feet ponderosa pine dominant
- Carbon emissions estimated 150,000 metric tons CO2 equivalent
- Evacuation orders affected 50 residents Loyalton area 48 hours
- Power outages to 200 customers Sierra Pacific Power 24 hours
- Road closures USFS Rd 07 total 10 miles 10 days
- Post-fire rehab treated 500 acres mulch/log erosion barriers
- Seedling mortality 90% in high severity patches
- Snag hazard created 2,000 standing dead trees >20" DBH
- Flood risk increased 20% peak flows modeled first 2 post-fire storms
- Noxious weed invasion potential high on 600 acres disturbed soil
- Air quality index peaked at 250 AQI Loyalton August 15
Impacts 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
- 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
- 5 helicopters including 2 Type 1 provided 150,000 gallons water/ retardant drop
- 2 air tankers (MAFFS) dropped 80,000 gallons over 12 missions on day 2
- 12 dozers constructed 18 miles of line by August 20
- 45 miles of hose laid total for structure protection
- 8 structure engines protected 25 homes on south flank
- Total aviation resources logged 250 hours over fire duration
- 3 hotshot crews anchored north flank containment
- Water tenders numbered 4, shuttling 50,000 gallons daily peak
- Overhead team included 25 ICT4/IC5 personnel
- Backhaul operations removed 10 tons of supplies post-containment
- Night shift crews of 100 personnel mopped up 5% daily
- Retardant use totaled 120,000 gallons from helitankers
- 15 miles of handline constructed on steep terrain >30%
- Demob started August 23 with 100 personnel released
- Total cost of suppression estimated at $5.2 million
- 2 Type 3 engines provided structure defense 24/7
- Infrared flights conducted 8 times, mapping 95% accuracy
- Peak dozer hours 200/day on August 17-18
- Total line constructed 35 miles at 8 ft width average
- Medical transports: 3 minor injuries treated on site
- Fuel reduction via firing ops covered 200 acres strategically
Suppression 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
- Reference 1INCIWEBinciweb.nwcg.govVisit source
- Reference 2WEATHERweather.govVisit source
- Reference 3FIREfire.ca.govVisit source
- Reference 4FSfs.usda.govVisit source
- Reference 5NIFCnifc.govVisit source
- Reference 6WRHwrh.noaa.govVisit source
- Reference 7MESOWESTmesowest.utah.eduVisit source
- Reference 8NCDCncdc.noaa.govVisit source
- Reference 9LANDFIRElandfire.govVisit source
- Reference 10SOUsou.eduVisit source
- Reference 11DROUGHTMONITORdroughtmonitor.unl.eduVisit source
- Reference 12PREDICTIVESERVICESpredictiveservices.nifc.govVisit source
- Reference 13FSfs.fed.usVisit source
- Reference 14SFCHRONICLEsfchronicle.comVisit source
- Reference 15LATIMESlatimes.comVisit source
- Reference 16BLMblm.govVisit source
- Reference 17SIERRACOUNTYsierracounty.ca.govVisit source
- Reference 18SIERRA PACIFICPOWERsierra pacificpower.comVisit source
- Reference 19USGSusgs.govVisit source
- Reference 20AIRNOWairnow.govVisit source