JSLALALAND

CITY & ITS PEOPLE

The LA weather forecast translator

In LA, someone will call 15°C (59°F) 'freezing.' This translates the forecast word by word: half funny (marine layer, microclimates), half seriously important (Santa Ana, Red Flag, evacuation terms). Save it before fire season.

Translated from Jasmine’s original Chinese. The illustrated slides are on the interactive reader.

Key points

Full text

  1. First, learn to convert: °F → °C

    Just remember three numbers: 59°F ≈ 15°C, 77°F ≈ 25°C, 95°F ≈ 35°C. The mental math is (°F − 30) ÷ 2, and the hotter it gets, the more the real number runs a little above your estimate.

  2. No.01｜"It's freezing!"

    What it really means: about 15°C (59°F). Downtown LA winter days average about 20°C (68°F), nights about 9°C (48°F); Taiwan's Central Weather Administration only calls it a cold air mass below 14°C (57°F), and a cold wave below 10°C (50°F).

  3. No.02｜Marine layer＋May Gray／June Gloom

    Low clouds drifting in off the ocean get trapped under warm air, rolling in at night and slowly burning off during the day. May and June mornings at the beach are solid gray, and even the NWS forecast says so; for blue sky, wait till noon or drive inland.

  4. No.03｜Microclimate

    Different areas can be wildly different on the same day: the August average high is about 25°C (77°F) at LAX and about 36°C (97°F) in Woodland Hills in the Valley. Don't just check the forecast for 'Los Angeles'; check the area you're going to.

  5. No.04｜Santa Ana winds

    Hot, dry winds blowing from the inland desert toward the coast, most common from October to March. Dry lips, lots of static, leaves rustling, and the most dangerous weather for LA wildfires.

  6. No.05｜Fire Weather Watch vs Red Flag Warning

    A Watch means dangerous fire weather is 'possible'; a Red Flag means it's 'happening now or coming right up.' When you see a Red Flag: no open flames outdoors, charge your phone, fill up the gas tank, watch for alerts.

  7. No.06｜PDS Red Flag Warning

    PDS = Particularly Dangerous Situation, a level more serious than Red Flag; the NWS issued it during the January 2025 Palisades and Eaton fires. When you see those three letters, take it seriously.

  8. No.07 | PSPS: Public Safety Power Shutoffs

    To prevent wildfires, the utility shuts off your power ahead of time. Around LA, that's SCE, usually with notice about two days and one day ahead; LADWP, in the City of LA, doesn't do these shutoffs. If SCE sends your power bill, sign up for alerts.

  9. No.08 | Evacuation terms

    Evacuation Warning = possible danger; if you need extra time or have pets, you can leave now. Evacuation Order = immediate danger, leave now. Shelter in Place = go inside, close the doors and windows, and stay put.

  10. No.09｜Atmospheric river

    A long, narrow band of moisture in the sky that brings heavy rain when it hits; CW3E ranks them in five levels, AR1 to AR5. The Pineapple Express is the kind that carries moisture from near Hawaii. Cute name, not-cute rain.

  11. No.10 | The words in your weather app

    "20% chance of rain" = a one-in-five chance it rains (at least a little) where you are, not that 20% of the area is getting rain. When Angelenos see 20%, they're already canceling plans.

  12. No.11 | When it's hot

    A Heat Advisory means very hot and dangerous; the most serious is an Extreme Heat Warning (called Excessive Heat before March 2025). The Valley and inland areas heat up first, so go out in the morning or evening.

  13. No.12 | Air quality, AQI

    Green 0–50 is good, yellow is moderate, orange 101–150 means sensitive groups should be careful, red 151+ is unhealthy for everyone. During wildfires, South Coast AQMD issues Smoke Advisories recommending you stay indoors.

  14. The two most misunderstood terms

    LA has a monsoon too: from late June to September, moisture comes up from Mexico and the mountains get afternoon thunderstorms. 'Earthquake weather,' says the USGS, doesn't exist; earthquakes are equally likely in any weather.

  15. The LA weather safety checklist (screenshot it)

    alert.lacounty.gov for emergency alerts, protect.genasys.com for your evacuation zone, SCE outage alerts, airnow.gov for air quality, weather.gov/lox for the official forecast, Caltrans QuickMap for road conditions.

  16. Two-city mirror

    Taipei's weather is something the whole island talks about together: typhoon days off, cold air masses, heavy rain warnings; LA's weather is different in every area. 'LA's weather rarely changes, but every time it does, it has a name.'

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An original JSLALALAND field guide by Jasmine Chang (@jslalaland).