ZIP code 91789

Los Angeles County, including Walnut, Industry, Diamond Bar and others

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Report created October 27, 2026 at www.firezones.info/zip/91789

  • Fire hazard severity zones

    Share of the land in each CAL FIRE hazard class

    17% Very High

    Most of the Very High land is in the Local Responsibility Area, where each city or county adopts the zones CAL FIRE recommends.

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  • Fire history

    Share of the land inside a recorded wildfire perimeter

    25% has burned

    Most recently the 2022 Cut Off Fire, which burned 2 acres here, one of 21 fires on record.

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  • Power line fire risk

    Share of the land in the High Fire-Threat District

    13% Elevated · 1% Extreme

    Utilities may shut off power in the CPUC High Fire-Threat District in fire weather, and homes outside it can lose power when their lines run through it.

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Land by hazard class

  1. Very High 1,724 acres · 341 state, 1,383 local 17%
  2. High 2,231 acres · <1 state, 2,231 local 22%
  3. Moderate 614 acres · <1 state, 614 local 6%
  4. Non-wildland 5,619 acres · Local Responsibility Area 55%

10,187 acres of land in all, 341 in the State Responsibility Area and 9,846 in the Local. State zones are the ones the State Fire Marshal designated, in effect since 1 April 2024. Local zones are CAL FIRE's 2025 recommendation, which each city or county adopts by ordinance and can make stricter. How to read fire zones

Largest fires

  1. 1972 Winnett Fire Of 747 acres in all 687 acres
  2. 1929 Ryan 116 Fire Of 543 acres in all 390 acres
  3. 1970 Fullerton Fire Of 3,381 acres in all 353 acres
  4. 1970 Winnet Fire 305 acres
  5. 1949 Citurs No. 174 Fire Of 517 acres in all 263 acres
  6. 1981 Sun Mountain Ranch Fire Of 197 acres in all 193 acres
  7. 1971 Gartel Fire 119 acres
  8. 1979 Unnamed fire Of 118 acres in all 116 acres
  9. 1928 Quinn 22 Fire 104 acres
  10. 1972 Buzzard Peak Fire Of 183 acres in all 98 acres

And 11 smaller fires. In all, 2,559 acres of ZIP code 91789 have burned. Acres are the land each fire burned here, and fires that crossed less than an acre are not counted. Some older or smaller fires may be missing, and a fire perimeter can include unburned patches. How to read fire history

Sources

Fire hazard severity zones
CAL FIRE Office of the State Fire Marshal
State map published 27 June 2025, local map 2 February 2026
Fire history
CAL FIRE Fire and Resource Assessment Program
Published 28 July 2026
Power line fire risk
California Public Utilities Commission
Published 23 February 2026

This site is independent and not affiliated with CAL FIRE or the CPUC, so for an official determination, check with the agency or your city or county. How we read the data

Nearby areas

Communities in ZIP code 91789

Neighboring ZIP codes

  1. 91789 17% Very High · this area
  2. 91724 29% Very High
  3. 91744 6% Very High
  4. 91748 45% Very High
  5. 91765 55% Very High
  6. 91768 18% High · 4% Very High
  7. 91773 33% Very High
  8. 91791 12% High · 1% Very High
  9. 91792 13% High