Understand clouds before conditions change

Characteristics: Cirrus clouds are made of ice crystals and look like fine white hair, hooks, or feathers.

Marine meaning: Good early cue to check tomorrow’s forecast, especially before an offshore trip.

Characteristics: Cirrocumulus appears as many small white grains or ripples, usually without shading.

Marine meaning: Not normally dangerous by itself, but monitor if it appears with other signs of an approaching front.

Characteristics: Cirrostratus is made of ice crystals and spreads like a transparent sheet across the sky.

Marine meaning: Use it as an early warning to check the next 24–48 hours of weather before longer passages.

Characteristics: Altostratus covers much of the sky. The sun may look like a pale disk behind the cloud.

Marine meaning: Good time to review the forecast, plan shelter, and check if wind will rise with the front.

Characteristics: Altocumulus clouds look like small rounded clumps, rolls, or ripples. They are larger than high cirrocumulus patches.

Marine meaning: Watch for building wind, humidity, and darker growing clouds later in the day.

Characteristics: Stratus clouds make the sky look flat and dull. They can sit very low and may produce mist or light drizzle.

Marine meaning: Watch visibility carefully near shore, traffic, buoys, and harbor entrances.

Characteristics: Stratocumulus clouds form broad, lumpy layers with gaps of brighter sky between them.

Marine meaning: Usually manageable for boating, though it may feel cool, grey, and breezy.

Characteristics: Nimbostratus covers most of the sky with a dark, flat, layered look. It often hides the sun completely.

Marine meaning: Expect wet decks, reduced visibility, and uncomfortable conditions over a longer period.

Characteristics: Cumulus clouds look like cotton balls with clear edges and flat bases. They usually form in rising warm air during the day.

Marine meaning: Generally fine for boating, but keep watching if the clouds build vertically or wind starts increasing.

Characteristics: Cumulonimbus clouds grow very tall, often with a dark base and a spreading anvil-shaped top. They are the classic thunderstorm clouds.

Marine meaning: Avoid open water if possible. Reef early, watch radar, and prepare for squalls, lightning, and steep short waves.