About MTR Fire Weather ✕

What is this?

A map-first fire weather dashboard for the NWS MTR (San Francisco Bay Area / Monterey Bay) Weather Forecast Office. It displays current observations from fire weather stations across the region, color-coded by severity, and lets you set a point of interest with distance rings to monitor conditions near a specific location.

Data source

Station observations are fetched from the Synoptic Data API, which aggregates real-time data from RAWS (Remote Automated Weather Stations), ASOS (Automated Surface Observing Systems), and several regional mesonet networks. Stations are filtered to the same network list used by the NWS MTR Fire Weather Snooper (network IDs 1, 2, 174, 229, 231, 139, 183, 265). Data is cached at the edge and refreshed every 10 minutes.

Severity Index

The Severity Index (SI) is computed using the formula published by the National Weather Service:

SI = Wind + 0.75 × (50 − RH) + 0.50 × (T − 70)

Wind is the higher of sustained wind speed and gust (mph), RH is relative humidity (%), and T is temperature (°F). The minimum value is 0. A score of 30 is considered significant; 100 is about as bad as it gets.

Red Flag & Flirting thresholds

Red Flag conditions are flagged when RH ≤ 20% and wind speed ≥ 15 mph simultaneously. Flirting stations are within 5% RH and 5 mph of both thresholds at the same time — close but not yet meeting criteria. These thresholds reflect standard NWS MTR fire weather criteria; actual issued Red Flag Warnings may incorporate additional factors including fuel moisture and forecast trends.

Disclaimer

This is an unofficial situational awareness tool. It is not affiliated with or endorsed by the National Weather Service, NOAA, CAL FIRE, or any fire agency. Always refer to official NWS products and your agency's operational channels for fire weather decisions.