Space WX Alerts: ALERT:  Geomagnetic K-index of 4 ( Latest Alert ) - Issue Time: 2023 Oct 01 0101 UTC
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55.9°F  72% CBI: 3 Chandler Burning Index Description
Fire Weather Index icons
Live FWI: 1.6
Fire Weather Index icons
Live FWI10: 1.6
Current Conditions for Foresthill, CA.
Updated10/3/23  12:02am
Current Lightning Map
Current Fire Danger

Fire locations are based on data provided by the National Interagency Coordination Center and are subject to change.

Move your mouse over the fire indicators to see additional information.

Today's Outlook
Day 1 Fire Weather outlook
Tomorrow's Outlook
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Day 3 through Day 8 Fire Weather outlook
Month 1 Outlook
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Fire Weather Warnings, and Watches

Map and data courtesy of #FireMappers. Learn more about #FireMappers here.

This map is not a source of official information. Do not use this map to make important decisions that could result in harm to life or property. Always follow the instructions of local law enforcement and officials. This map is intended only to provide a general awareness of wildfire activity. For official information regarding the incidents shown on the map, please visit

Fire Information - National Fire News

Northern California Preparedness Level 2  

National Preparedness Level 2   

Updated Time: October 2, 2023

Five new large fires were reported over the weekend, two in Mississippi, and Arizona, Colorado and Texas each had one. Thirty-five large wildfires have burned 381,593 acres in 11 states. About 4,500 wildland firefighters and support personnel are assigned to incidents nationwide. To date, 45,192 wildfires have burned 2,467,748 acres nationwide.

During hunting season, dirt bikes, ATVs, and side-by-side vehicles are used to travel to hard-to-get places. If your plans for getting outside include some motorized adventure, please be cautious when driving or parking on dry grass or brush.  It's also important to be aware of animal habitats including water and food sources, nesting areas and sensitive terrain. Never chase animals or shoot a firearm from a vehicle. Please hunt and recreate responsibly this fall.

The predictive services staff at the National Interagency Coordination Center released the National Significant Wildland Fire Potential Outlook for September through December. The current wildland fire potential outlook and the monthly seasonal outlook podcast is also available.

The Federal Emergency Management Agency (FEMA) continues to work with state and local agencies in Hawai‘i. Some national parks in Hawai‘i have been affected by wildfires. For the latest on closure status, recovery, and travel please visit: Wildfires affecting Hawaii - Hawai'i (U.S. National Park Service) (

Please check the IMSR for more information.
National Weather: October 2, 2023

A deep upper-level trough will continue to move eastward across the Intermountain West, with an associated cold front moving onto the High Plains this evening and overnight. Moist, southerly flow will overspread the southern and Colorado Rockies onto much of the High Plains from southwest Texas through the western Dakotas. Scattered thunderstorms are expected across these areas, with more widespread thunderstorm coverage over eastern New Mexico, including severe thunderstorms. Farther to the east, relative humidity will drop down to 20-35% across much of the Southeast, Texas, and southern into the central Plains, with breezy easterly to southerly winds. Scattered thunderstorms are expected over south Texas and Florida, while the rest of the central and eastern US remains rain-free with above normal temperatures. Below normal temperatures will continue for the West, and scattered precipitation is expected from the Pacific Northwest through the central and eastern Great Basin and much of the Rockies, including snow above 7,500 feet. 

Local Weather: Monday, October 2, 2023 - 1:47pm PDT
Elevated Fire Weather Conditions Midweek

Lightning Ignited Fires

National Interagency Fire Center statistics show that in 2002-2006, an average of 12,000 (16%) of the wildland fires were started by lightning per year. These fires burned an average of 5.2 million acres per year.

   Two-thirds of lightning fires occur June-August. lightning fires peak in the late afternoon and early evening. Three-fifths (61%) of all fires started by lightning occurred between 2:00 and 10:00 p.m.

   55% of lightning fires occur outdoors, and 41% occur in structures. Deaths and injuries occur mostly in structures (89% and 86%, respectively).

   Because most lightning fires occur outdoors, the most prominent form of material ignited is "growing living form," which includes trees, brush, and grass. Materials found on residential structures that are commonly ignited include roofs, sidewalls, and framing. Electrical wiring is another material often ignited, as the electrical current in lightning is drawn to electrical wires.

   Civilians suffer more injuries than fatalities in lightning fires each year. Most casualties result from lightning structure fires rather than outside or other types of lightning fires. 89% of lightning fire civilian fatalities and 86% of injuries occur in structure fires.

Potential Outlook Maps

Fire Potential Outlook

Significant Fire Potential Outlooks
(click for more info)
Lightning Probability Forecast Map
Thunderstorm Probability
Current Lightning Efficiency Map
(click to enlarge)

Lightning Ignition Efficiency

Lightning fires are started by strikes to ground that have a component called a continuing current. All positive discharges have a continuing current, and about 20% of negative discharges have one. Ignition depends on the duration of the current and the kind of fuel the lightning hits. Ignition in fuels with long and medium length needle cast, such as Ponderosa pine and Lodgepole pine, depend on the fuel moisture. Ignitions in short- needled species, such as Douglas fir depend far more on the depth of the duff layer than on the moisture. Spread of the fire after ignition usually depends on fuel moisture in all cases.

The ignition efficiency on a 1 km pixel is given on a per discharge basis. That is, if the efficiency is high, then about 9 discharges will result in one ignition; if the efficiency is extreme, about 5 or fewer discharges will result in an ignition. The ratio of positive and negative discharges is built into the calculation. (Latham and Schlieter 1989) document the algorithm.

The fuel type and depth are conversions of the 1 km resolution current cover type (Hardy and others 1999) for this specific calculation. The moisture input is the 100-hr dead fuel moisture.

August 2002 - The lightning ignition efficiency algorithm has been corrected due to discovery of an error. The resulting maps reflect higher lightning efficiency than previously.

Current Lightning Efficiency Map
Current Lightning Efficiency Map

Haines Index (Wildfire Potential)

Haines (1988) developed the Lower Atmosphere Stability Index, or Haines Index, for fire weather use. It is used to indicate the potential for wildfire growth by measuring the stability and dryness of the air over a fire. It is calculated by combining the stability and moisture content of the lower atmosphere into a number that correlates well with large fire growth. The stability term is determined by the temperature difference between two atmospheric layers; the moisture term is determined by the temperature and dew point difference. This index has been shown to be correlated with large fire growth on initiating and existing fires where surface winds do not dominate fire behavior.

Haines Index is computed from the morning (12Z) soundings from RAOB stations across North America.

The Haines Index can range between 2 and 6. The drier and more unstable the lower atmosphere is, the higher the index.

  • 2 : Very Low Potential -- (Moist Stable Lower Atmosphere)
  • 3 : Very Low Potential
  • 4 : Low Potential
  • 5 : Moderate Potential
  • 6 : High Potential ------ (Dry Unstable Lower Atmosphere)
Current Haines Index Map
Haines Index Map

Fire Danger Maps

Each day during the fire season, national maps of selected fire weather and fire danger components of the National Fire Danger Rating System are produced by the Wildland Fire Assessment System (WFAS-MAPS), located at the USDA Forest Service Rocky Mountain Research Station in Missoula, Montana.

Current Observed Fire Danger Map
Observed Fire Danger Map
Current Forecast Fire Danger Map
Forecast Fire Danger Map
Current Observed Relative Humidity
Observed Relative Humidity
Current Observed Dew Point Levels
Observed Dew Point Levels
Current Observed Temperature
Observed Temperature
Forcast Wind Speed
Forcast Wind Speed

Keetch-Byram Drought Index

  Keetch and Byram (1968) designed a drought index specifically for fire potential assessment. It is a number representing the net effect of evapotranspiration and precipitation in producing cumulative moisture deficiency in deep duff and upper soil layers. It is a continuous index, relating to the flammability of organic material in the ground.

  The KBDI attempts to measure the amount of precipitation necessary to return the soil to full field capacity.

It is a closed system ranging from 0 to 800 units and represents a moisture regime from 0 to 8 inches of water through the soil layer. At 8 inches of water, the KBDI assumes saturation. Zero is the point of no moisture deficiency and 800 is the maximum drought that is possible. At any point along the scale, the index number indicates the amount of net rainfall that is required to reduce the index to zero, or saturation.

  The inputs for KBDI are weather station latitude, mean annual precipitation, maximum dry bulb temperature, and the last 24 hours of rainfall. Reduction in drought occurs only when rainfall exceeds 0.20 inch (called net rainfall). The computational steps involve reducing the drought index by the net rain amount and increasing the drought index by a drought factor.

Current - Keetch-Byram Drought Index
Keetch-Byram Drought Index


  • KBDI = 0 - 200: Soil moisture and large class fuel moistures are high and do not contribute much to fire intensity. Typical of spring dormant season following winter precipitation.
  • KBDI = 200 - 400: Typical of late spring, early growing season. Lower litter and duff layers are drying and beginning to contribute to fire intensity.
  • KBDI = 400 - 600: Typical of late summer, early fall. Lower litter and duff layers actively contribute to fire intensity and will burn actively.
  • KBDI = 600 - 800: Often associated with more severe drought with increased wildfire occurrence. Intense, deep burning fires with significant downwind spotting can be expected. Live fuels can also be expected to burn actively at these levels.

Chandler Burning Index Calculation
(0 - 120°F)
Relative Humidity
(0 - 100%)

Chandler Burning Index Fire Danger
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