Weather Effects

Knowledge of weather is the key to successful Rx burning, and is mandatory for proper management of smoke produced by burning.

An understanding of weather and its effects on fire is essential to any Rx burn. The more important elements to consider for executing a good burn are:

  • Wind
  • Relative Humidity
  • Temperature
  • Rainfall

Good winter Rx burning conditions often exist for several days after the passage of a cold front that brings ¼ to ¾ inch of rain. During this time, persistent winds, low relative humidities, cool temperatures and sunny days can be anticipated. Weather conditions for summer burning are much less predictable but summer burns can be successful with careful planning.

Sources of weather information

  • Georgia Forestry Commission (GFC) fire weather forecast
  • Media (television, radio, newspaper)
  • National Weather Service
  • Local Observation
  • Private Weather Forecasting Services

Preferred weather conditions

  • Wind - in-stand wind speeds 3- 5 mph
  • Humidity - 30-55 percent
  • Temperature (winter) - below 60 degrees Fahrenheit
  • Fine fuel moisture - 10 to 20 percent (see GFC fire weather maps )
  • Keetch-Byram Drought Index (KBDI) between 250 and 400

KBDI is the measure of moisture in the duff or upper soil layers. It ranges from 0 (very wet) to 800 (drought conditions). Low KBDI relates to very wet conditions, which would make it difficult for a fire to carry in the understory. High KBDI readings relate to dry conditions and may cause the fire to burn too deeply into the duff layer causing damage to root systems as well as possible soil damage. See GFC fire weather maps for up to date KBDI reading.