Gusts vs sustained wind, and why the gap matters

Wind is never perfectly steady, so forecasts give two numbers.

• Sustained wind is an average. In US weather observations it is measured over about two minutes.
• Gusts are brief peaks lasting a few seconds. A forecast gust is the strongest short burst expected in that hour.

Why the gap matters

The gust spread, gusts minus sustained, tells you how lumpy the wind will be. A day at 12 kt gusting 15 is steady and predictable. A day at 8 kt gusting 20 has long lulls punctuated by hard puffs that can knock a dinghy flat, spin a paddleboard sideways, or swing a boat into a dock.

On inland lakes the spread is often larger than on open water at sea. Hills, trees and buildings around the shore break the airflow up, and warm afternoon air mixes faster wind down from aloft in bursts.

Rules of thumb

• A spread under about 5 kt is steady.
• 5 to 10 kt is normal for a breezy afternoon on most lakes.
• More than 10 kt is gusty. Reef early, stay closer to shore in a kayak, and leave extra room when docking.

Lakeglance shows both numbers for every hour, draws the gust as a tick above each bar in the hourly strip, and lowers the score when the spread runs more than 8 kt.