RISINGNIFC, NOAAFebruary 2026🇺🇸 USSafety & Environment
🔥

Wildfire Risk Escalating — Record Fire Weather Conditions Across Western US

Record drought and extreme temperatures have pushed the Fire Weather Index to dangerous levels across the Western US. Understanding fire weather conditions helps homeowners, first responders, and land managers prepare. This calculator estimates fire risk based on temperature, humidity, wind, and drought conditions.

Concept Fundamentals
7.5M+
Acres Burned
2025 US total
Extreme
FWI Level
Western states
18K+
Structures Lost
2025 total
$6.3B
Cost
Suppression 2025

Ready to run the numbers?

Why: Record drought and extreme temperatures have pushed the Fire Weather Index to dangerous levels across the Western US. FWI >30 indicates extreme fire danger; Red Flag Warnings often align with FWI >20. Understanding fire weather helps homeowners, first responders, and land managers prepare for evacuation and defensible space.

How: The calculator uses the Canadian FWI system: FFMC (fine fuel moisture), DMC (duff moisture), DC (drought code) from temperature, humidity, precipitation, and previous-day values. ISI combines FFMC and wind for spread potential. BUI combines DMC and DC for fuel availability. FWI = f(ISI, BUI) gives overall fire intensity. Danger classes: Low (0-5), Moderate (5-10), High (10-20), Very High (20-30), Extreme (30+).

FFMC, DMC, DC moisture codes from weather inputsISI (Initial Spread Index) and BUI (Buildup Index)
Methodology
🌡️Weather Inputs
Temperature, humidity, wind, precipitation, previous-day moisture codes
🔥FWI Components
Six-component Canadian system: FFMC, DMC, DC, ISI, BUI, FWI
📊Visual Breakdown
Radar chart, component bar, moisture vs behavior doughnut
Sources:Natural Resources CanadaNWCG CFFDRS

Run the calculator when you are ready.

Calculate Fire Weather RiskAssess wildfire danger based on weather conditions

Weather (noon observation)

Previous Day Moisture Codes

fwi_calc.sh
CALCULATED
$ fwi_calc --temp=28 --rh=25 --wind=35 --precip=0
FWI
110.7
Danger Class
Extreme
Rate of Spread
Very fast — extreme fire behavior
Intensity Class
Extreme (6+)
FFMC: 93.1
DMC: 106.1
DC: 0.0
ISI: 38.7
BUI: 103.8
FWI: 110.7
Share:
Fire Weather Index
110.7
Extreme
Very fast — extreme fire behavior
numbervibe.com/calculators/trending/fire-weather-index-calculator

🌡️ Fire Danger Level

Low (0-5)Moderate (5-12)High (12-24)Very High (24-40)Extreme (40+)

📚 Historical Fire Event Comparison

How current conditions compare to conditions during major fires

Black Saturday (2009)
FWI: 120
Victoria, AU
Camp Fire (2018)
FWI: 55
Paradise, CA
LA Wildfires (2025)
FWI: 45
Los Angeles, CA
Fort McMurray (2016)
FWI: 38
Alberta, CA
Your Conditions
FWI: 110.7
← You

FWI Component Radar

Component Breakdown

Moisture vs Fire Behavior

📐 Calculation Breakdown

FUEL MOISTURE
FFMC (Fine Fuel Moisture)93.1
DMC (Duff Moisture)106.1
DC (Drought Code)0.0
FIRE BEHAVIOR
ISI (Initial Spread Index)38.7
BUI (Buildup Index)103.8
RESULT
FWI (Fire Weather Index)110.7
Danger ClassExtreme

For educational and informational purposes only. Verify with a qualified professional.

Quick Answer

The Canadian FWI system uses six components: FFMC, DMC, DC (moisture codes), ISI, BUI, FWI (fire behavior). FWI > 30 = Extreme danger; Red Flag Warnings often align with FWI > 20. Input temperature, humidity, wind, precipitation, and previous-day moisture codes to calculate.

FWI Component Breakdown

FFMC

Fine Fuel Moisture

DMC

Duff Moisture

DC

Drought Code

ISI

Initial Spread

BUI

Buildup Index

FWI

Fire Weather Index

📋 Key Takeaways

  • • The Canadian FWI system uses six components: FFMC, DMC, DC (moisture), ISI, BUI, FWI (fire behavior).
  • • Default seasonal start-up: FFMC=85, DMC=6, DC=15 (third day after snow leaves).
  • • FWI >30 = Extreme danger; Red Flag Warnings often align with FWI >20.
  • • Climate change has extended fire seasons — LA-area fires now occur year-round.

💡 Did You Know?

🇨🇦The FWI system was developed in Canada (Van Wagner 1987) and is now used in the US, Australia, Europe, and beyondSource: Natural Resources Canada
🔥Santa Ana winds can push FWI above 40 — the 2018 Woolsey Fire had FWI values exceeding 50Source: CAL FIRE
📅Seasonal start-up: calculations begin the third day after snow leaves, or third day with temp >12°CSource: NWCG
🌡️FFMC represents ~16-hour timelag fuels; DC represents ~53-day timelag — deep droughtSource: Van Wagner 1987
🚩Red Flag Warnings are issued when FWI, wind, and humidity combine for critical fire weatherSource: NWS
🏠Defensible space of 100 feet can reduce home ignition by 75% in wildfiresSource: NFPA
🌲Prescribed burns reduce fuel loads — lowering DMC/DC equivalents and fire intensity when wildfires occurSource: USFS

📖 How Does the FWI System Work?

Fuel Moisture Codes: FFMC (fine fuels), DMC (duff/organic), DC (deep drought). Higher = drier. DMC and DC use month-based day-length factors.

Fire Behavior Indices: ISI combines FFMC + wind (spread potential). BUI combines DMC + DC (fuel available). FWI = f(ISI, BUI) gives overall intensity.

Danger Classes: Low (0-5), Moderate (5-10), High (10-20), Very High (20-30), Extreme (30+).

🎯 Expert Tips

Evacuation Planning

Know your evacuation route. When FWI >20, have a go-bag ready. Check AQI for smoke exposure.

Defensible Space

Clear 30-100 ft around structures. Remove dead vegetation, trim trees. Create fuel breaks.

Red Flag Days

Avoid outdoor burning, equipment that sparks. Have water and tools ready. Monitor official alerts.

Prescribed Burns

Conduct when FWI is moderate (5-10) — enough to carry fire but controllable. Never in Extreme.

⚖️ FWI Danger Class Reference

FWI RangeDanger ClassFire Behavior
0-5LowControlled burn conditions
5-10ModerateControlled burn conditions
10-20HighActive surface fire
20-30Very HighRapid spread, crown fire potential
30-∞ExtremeCrown fires, spot fires, erratic behavior

❓ Frequently Asked Questions

What is the Fire Weather Index?

The FWI is a Canadian system that rates fire danger from weather. It outputs six components: FFMC, DMC, DC (moisture), ISI, BUI, FWI (behavior). Used worldwide.

What are FFMC, DMC, and DC?

FFMC = Fine Fuel Moisture Code (litter, 16-h timelag). DMC = Duff Moisture Code (organic layer, 15-day). DC = Drought Code (deep soil, 53-day).

What is a Red Flag Warning?

NWS issues when low humidity, high wind, and dry fuels combine for critical fire weather. Often corresponds to FWI >20.

How does climate change affect fire season?

Longer droughts, warmer temps, and earlier snowmelt extend fire season. LA-area now sees significant fire risk year-round.

What is defensible space?

Cleared area around structures (30-100 ft) that reduces ignition from radiant heat and embers. Can reduce home loss by 75%.

When are prescribed burns done?

Typically when FWI is Moderate (5-10) — enough moisture to control, dry enough to carry fire. Never in Extreme.

What are Santa Ana winds?

Dry, offshore winds in Southern California. Can push RH below 10%, wind 50+ mph — FWI often exceeds 40.

How do I get real-time FWI?

Canadian Wildland Fire Information System (CWFIS), US NWS Fire Weather, and state fire agencies publish daily FWI maps.

📊 FWI by the Numbers

0-5
Low
5-10
Moderate
10-20
High
30+
Extreme

⚠️ Disclaimer: This calculator uses the Canadian FWI system (Van Wagner 1987). For official fire danger, use CWFIS, NWS, or local fire agencies. Not a substitute for evacuation orders or official warnings.

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