Fire Danger Guide¶

Weather Station Core implements three regional fire danger systems. All three run from your weather station data with no external API calls.

System overview¶

System	Region	Standard	Inputs
Canadian FWI	Global (origin: Canada)	Van Wagner (1987)	Temp, RH, wind, 24h rainfall
McArthur FFDI	Australia	Noble et al. (1980)	Temp, RH, wind, drought factor
Fosberg FFWI	US / global	Fosberg (1978)	Temp, RH, wind

All three are enabled together via the Fire Risk feature toggle.

Enabling fire danger¶

During setup: enable Fire Risk on the Features step.

After setup: Settings → Devices & Services → Weather Station Core → Configure → Features → Fire Risk, or toggle switch.ws_enable_fire_risk_score on the device page.

Canadian Fire Weather Index (FWI)¶

The FWI system (Van Wagner 1987) is the most comprehensive of the three. It models fuel moisture at three depths and derives an index of fire intensity.

Moisture codes¶

Sensor	What it models	Time constant
`sensor.ws_fwi_ffmc`	Fine dead fuels, litter, surface grass	~24 hours
`sensor.ws_fwi_dmc`	Loosely compacted duff, 5-10 cm depth	~12 days
`sensor.ws_fwi_dc`	Deep compact organic layer, > 10 cm	~52 days

Moisture codes are updated once per calendar day and persist across HA restarts. They self-correct within a few days from the Van Wagner (1987) standard start values.

Derived indices¶

Sensor	Description
`sensor.ws_fwi_isi`	Initial Spread Index — expected initial fire spread rate
`sensor.ws_fwi_bui`	Buildup Index — total available fuel
`sensor.ws_fwi`	Fire Weather Index — intensity of a spreading fire
`sensor.ws_fwi_dsr`	Daily Severity Rating — operational difficulty of fire control

The sub-components (FFMC, DMC, DC, ISI, BUI) are enabled separately via enable_fwi_components to reduce entity count if you only need the composite FWI and DSR.

Display scale¶

sensor.ws_fire_risk_score maps the FWI to a 1-10 display scale:

FWI	Fire danger	Score
< 5	Very Low	1
5-11	Low	2
12-21	Moderate	3-4
22-32	High	5-6
33-49	Very High	7-8
≥ 50	Extreme	10

McArthur Fire Danger Index (FFDI)¶

Used operationally in Australia by the Bureau of Meteorology. Computed from temperature, relative humidity, wind speed, and the FWI drought factor (which approximates soil moisture depletion).

sensor.ws_ffdi — values above 50 correspond to Catastrophic (Code Red) conditions in the Australian rating system.

Fosberg Fire Weather Index (FFWI)¶

A simpler index used by NOAA and the US Forest Service. Combines a moisture content estimate from temperature and relative humidity with wind speed to produce a 0-100 scale of fire weather severity.

sensor.ws_ffwi — values above 50 indicate extreme fire weather conditions.

Automation: fire danger alert¶

See Blueprints for the fire_danger_alert.yaml blueprint that sends a notification when sensor.ws_fire_risk_score reaches a threshold.

Example manual automation:

trigger:
  - platform: numeric_state
    entity_id: sensor.ws_fire_risk_score
    above: 6
condition:
  - condition: time
    after: "07:00:00"
    before: "22:00:00"
action:
  - service: notify.mobile_app_phone
    data:
      title: "Fire danger alert"
      message: >
        Fire risk score: {{ states('sensor.ws_fire_risk_score') }}/10.
        FWI: {{ states('sensor.ws_fwi') }}.

Disclaimer¶

These sensors are informational only and are not suitable for operational fire weather decisions. Consult your national fire service, Bureau of Meteorology (Australia), or equivalent authority for official fire danger ratings.

References: - Van Wagner, C.E. (1987). Development and structure of the Canadian Forest Fire Weather Index System. Forestry Technical Report 35. Canadian Forestry Service. - Fosberg, M.A. (1978). Weather in wildland fire management: the fire weather index. In: Proceedings: Conference on Sierra Nevada Meteorology. - Noble, I.R., Bary, G.A.V., Gill, A.M. (1980). McArthur's fire-danger meters expressed as equations. Australian Journal of Ecology, 5, 201-203.