Sound travels one mile in about 5 seconds. Therefore, if you see a lighting bolt and hear the thunder 25 seconds later, you can estimate the storm is about 5 miles away. If drift and debris are flowing down the middle of the river channel, the river or creek is still rising. When the debris begins settling to the edges, it is receding or falling. Grapefruit 4.00 inches Softball or larger 4.50 inches Estimating Wind Speeds with Visual Clues Beaufort number Description Speed Visual Clues and Damage Effects 0 Calm Calm Calm wind.
Smoke rises vertically with little if any drift.
1 Light Air 1 to 3 mph Direction of wind shown by smoke drift, not by wind vanes. Little if any movement with flags. Wind barely moves tree leaves. 2 Light Breeze 4 to 7 mph Wind felt on face. Leaves rustle and small twigs move.