Welcome & Learning Objectives
This course is built around key concepts from S-290 Intermediate Wildland Fire Behavior and focuses them on prescribed fire planning and implementation.
Read Weather
Identify important forecast and observed weather elements that affect burn windows, holding, smoke, and safety.
Apply Prescription
Compare weather, fuel moisture, wind, and smoke conditions against the burn plan prescription.
Make Decisions
Use observations and trends to continue, pause, modify, or stop prescribed fire operations.
Course outcome: Students should be able to interpret weather information, recognize warning signs, document observations, and support Burn Boss decision making.
Module 1: The Fire Environment
The wildland fire environment is shaped by the interaction of weather, topography, and fuels. Weather is the most variable component and can change quickly during prescribed fire operations.
Weather Factors
TemperatureRelative HumidityAtmospheric StabilityWind Speed & DirectionPrecipitationPrescribed Fire Use
Weather controls whether a burn is too cool to meet objectives, within prescription, or too hot for safe implementation.
Ask: Is the weather helping us meet objectives, or pushing us toward escape potential?
Interactive Fire Environment Simulator
42Fire Behavior Potential
ModSpread Concern
GoodHolding Outlook
ReviewDecision
Module 2: Temperature & Relative Humidity
Temperature and relative humidity usually move opposite each other during the day. As temperature rises, RH often drops. That can dry fine fuels and increase ignition probability, flame length, and holding difficulty.
Prescribed Fire Application
- Morning: Higher RH, cooler fuels, better holding, may be too cool to meet objectives.
- Afternoon: Lower RH, warmer fuels, more active fire behavior, higher escape potential.
- Evening: Recovery may support mop-up and patrol, but drainage winds may change smoke impacts.
Quick Decision
Your burn plan prescription is RH 25–55%. At 0900, RH is 63%. At 1300, RH is forecast at 31% with light winds. What is the best interpretation?
Module 3: Wind Systems
Wind is often the strongest short-term driver of prescribed fire behavior. Track both speed and direction, and distinguish between forecast wind, 20-foot wind, eye-level wind, mid-flame wind, gusts, and local terrain-driven winds.
| Wind Type | Why It Matters | Prescribed Fire Watch-Out |
|---|---|---|
| Slope winds | Daytime upslope and nighttime downslope flows can change fire spread and smoke movement. | Watch for afternoon upslope increase and evening drainage smoke. |
| Valley winds | Can channel fire and smoke along drainages. | Wind direction may not match nearby forecast point. |
| Frontal winds | Can bring rapid direction shifts and stronger gusts. | Pause ignition ahead of expected frontal passage. |
| Thunderstorm outflow | Can arrive suddenly and from unexpected directions. | Stop ignition and prepare for rapid spread/spotting. |
Prescribed fire rule: A wind shift can turn a secure flank into a head fire. Re-check holding points, escape routes, and smoke impacts whenever wind direction changes.
Module 4: Atmospheric Stability & Smoke
Atmospheric stability influences vertical mixing, convection column development, and smoke dispersion. Stable conditions can trap smoke near the ground; unstable conditions can increase convection and fire behavior.
Stable / Inversion
Reduced vertical mixing, smoke pooling, lower surface wind, and potential for sudden increase when inversion breaks.
Unstable
Better vertical mixing but more active fire behavior, stronger convection, and increased spotting potential under the wrong conditions.
Smoke Management Terms
Mixing HeightTransport WindVentilationDispersionClearing IndexSmoke Sensitive ReceptorsScenario
A grass understory burn is planned near a highway. Morning inversion is holding smoke low in the drainage. Forecast says mixing improves after 1100. What is the best action?
Module 5: Forecasts, Spot Forecasts & RAWS
Prescribed fire planning should compare forecast information with nearby observations and on-site readings. A spot forecast is site-specific and should include the project location, fuel type, observations, and requested forecast elements.
Before the Burn
- Review Fire Weather Planning Forecast
- Request a Spot Weather Forecast
- Review Red Flag Warnings / Fire Weather Watches
- Check nearby RAWS trends
- Compare forecast to prescription
During the Burn
- Take on-site observations
- Track wind shifts and gusts
- Record temp/RH trends
- Watch smoke movement
- Brief changes to Burn Boss and holding resources
Spot Forecast Request Builder
Module 6: Taking & Documenting Weather Observations
On-site weather observations verify whether the forecast matches the burn unit. Observations should be taken before ignition, during ignition, when conditions change, and as directed by the Burn Boss.
Observation Log
| Time | Temp | RH | Wind | Clouds/Smoke | Notes |
|---|---|---|---|---|---|
Minimum observation elements: time, location, temperature, relative humidity, wind speed, wind direction, cloud cover, smoke behavior, and any notable changes.
Module 7: Fuel Moisture & Prescription Windows
Fine fuels respond quickly to changing weather. A small drop in RH combined with wind can move a burn from low-intensity backing fire to active head fire behavior.
Fuel Moisture Concepts
1-hour fuels10-hour fuels100-hour fuelsLive fuel moistureCuringShadingPrescription Checker
Example prescription: Temp 55–85°F, RH 25–55%, Mid-flame wind 2–10 mph, Fine dead fuel moisture 6–12%.
Within prescription. Continue monitoring.
Module 8: Extreme Fire Behavior Warning Signs
Prescribed fire crews must identify conditions that can rapidly push fire behavior outside the plan. Warning signs include increasing winds, dropping RH, unstable atmosphere, poor overnight recovery, plume growth, frequent spotting, and unexpected fire intensity.
Weather
- Gusty shifting winds
- Cold front or thunderstorm nearby
- Rapid RH drop
- Inversion lifting
Fuels
- Fine fuels fully cured
- Low dead fuel moisture
- Vertical continuity
- Heavy loading near line
Fire Behavior
- Spotting over line
- Increasing flame length
- Fire whirls
- Torching or crown involvement
Action trigger: When observed fire behavior no longer matches the expected fire behavior in the burn plan, stop and reassess before continuing ignition.
Module 9: Burn Boss Weather Decision Scenario
Scenario: Oak Woodland Underburn
Prescription: Temp 55–82°F, RH 28–55%, Mid-flame wind 2–8 mph, transport winds away from town, no Red Flag Warning.
Current: 1100 temp 68°F, RH 42%, mid-flame wind 3–5 mph from SW. Smoke lifting well. Forecast: RH drops to 24% after 1500, gusts to 16 mph possible after 1600.
What is the best operational decision?
Write Your Weather Briefing
Final Exam
Answer the questions below. A score of 80% or higher unlocks a certificate of completion.
Certificate of Completion
This certifies completion of
Fire Weather for Prescribed Fire
Score:
Date: