Weather and fire behavior: Wind

A critical consideration for planning and conducting a burn is wind direction and speed. Prevailing wind directions are usually from the southwest, northwest or southeast, and can vary with the season and passing fronts. However, the best wind direction may be determined by features outside the burn area such as roads, houses, airports and powerlines. A wind direction should be selected that will carry smoke away from nearby hazards. Localized wind directions and behavior can be changed by tree lines, hills or drainages. They need to be monitored before and during the burn.

Most prescribed burns should be done with a reported wind speed of 5 to 15 mph. Wind speeds given by weather reports and those listed in MDC and NRCS burn plans are measured at 20 feet above ground. At eye level, called the mid-flame wind speed, the wind speed is roughly half of the 20-foot wind speed. A 5-15 mph 20-foot wind speed usually does not shift direction. A prescribed fire under these wind speeds will be more predictable. Wind shifts are common at speeds of less than 5 mph and the drift of the smoke column is less predictable. Wind speed usually increases toward mid-day as the temperature increases.