National Weather Service United States Department of Commerce

Heavy Rain in Florida; Dry, Windy Conditions in the Central Rockies

Increased thunderstorm activity and locally heavy rainfall may produce flooding in Florida. Locally heavy rain is also possible near the Upper Great Lakes, Great Basin and New Mexico into west Texas. Heavy snow is expected in the central and southern Sierra Nevada. A dry and windy air mass will bring critical fire weather conditions to parts of the eastern Great Basin and central Rockies. Read More >

Definitions of a Fire Weather Watch and a Red Flag Warning

A Fire Weather Watch or Red Flag Warning is issued when the combination of dry fuels and weather conditions support extreme fire danger. These products are written for land and fire managers to highlight the increased fire danger.

Each NWS office creates local criteria for fire weather watches and red flag warnings. The criteria for northern Illinois and northwest Indiana include:

  1. Sustained 20 foot winds of 20 mph or higher.
  2. Afternoon relative humidity less than 25%.
  3. 10 hour fuel moisture at 8% or less for one day.

A Fire Weather Watch is issued up to 72 hours before the above conditions are expected to occur.

A Red Flag Warning is issued when the conditions above are expected to occur or are occurring within the next 24 hours.

Click to get to the NWS Chicago Fire Weather Page