Significant weather — how to read it

The significant weather map shows the dominant weather phenomenon per grid cell as a WMO WW code — fog, drizzle, rain, snow, freezing precipitation, thunderstorms, hail. It's finer than the precipitation map because it distinguishes hazard type.

What the colors and emoji mean

• Fog / mist — grey shading. Visibility problem, ceiling irrelevant. Cross-check with the visibility map.
• Drizzle — light blue. Usually low ceiling, poor visibility, but manageable.
• Rain — blue → green shades by intensity. Standard VFR concern; check ceiling.
• Snow — light violet. Winter operations: runway conditions, icing risk on climb.
• Freezing rain / drizzle — pink / magenta. Airframe-icing emergency. Do not depart, do not descend into it.
• Ice pellets — a specific pink. Indicates a warm layer aloft over a subfreezing surface; freezing rain often coexists nearby.
• Thunderstorm — red/orange with a ⛈️ marker. Combine with CAPE and simulated radar.
• Thunderstorm with hail — dark red / purple. Serious; hail cores can extend well outside the visible cloud.

Hover / tap for the code

Each cell surfaces its WMO WW code on hover (desktop) or tap (mobile). The code disambiguates similar-looking colors — e.g. WW 71 (light continuous snow) vs. WW 85 (light snow shower). Codes 60-69 are rain, 70-79 are solid precipitation, 80-89 are shower type, 90-99 are thunderstorm codes.

The freezing-precipitation trap

Freezing rain is the single most dangerous weather this map surfaces for GA aircraft. A pink patch on your route inside the 0°C to +5°C layer means an airframe that will pick up ice faster than your de-ice can shed it — assuming you have de-ice at all. Treat any pink patch as a hard no-go unless you have a specific plan to stay above or below the warm-nose layer.