National Weather Service United States Department of Commerce

Hazardous Heat Across the Western U.S.; Heavy Rain and Flooding in the Southwest and Western Gulf Coast

Dangerous heat will persist over portions of interior California, the Great Basin, and the northern Rockies through Thursday. Heat will gradually spread into the northern Plains today. Across the western Gulf Coast, heavy to excessive rainfall will persist through mid-week. Additionally, the Southwest Monsoon will continue to bring a flash flooding threat to the Four Corners Region this week. Read More >


Based on our research and feedback from the ranching community, the following were identified as hazardous weather elements that increased risk of problems or death to exposed newborns:

  • Wind chill
  • Rain or Wet Snow
  • High Humidity (because it makes it more difficult to dry off the animal)
  • Combinations of these elements (such as windchill and rain) are particularly dangerous
  • Sunshine vs. Cloudy Days

The criteria used to generate the forecasts from the tab above is seen below:

  • NONE: Wind Chill above 41 degrees
  • SLIGHT: Wind Chill less than 41 degrees for 2 or more hours
  • MILD: Wind Chill less than 32 degrees for 2 or more hours
  • MODERATE: Wind Chill less than 0 degrees for 2 or more hours or Wind Chill less than 36 degrees and .02" precipitation
  • SEVERE: Wind Chill of -9 degrees or colder for two or more hours, or wind chill of less than 34 degrees and .05" of precipitation
  • EXTREME: Wind Chill of -18 or colder for two or more hours, or wind chill less than 32 degrees and .1" of precipitation
  • For sunny conditions (Cloud cover less than 40%), reduce SLIGHT-EXTREME by one category
  • For humid conditions (Minimum relative humidity's remaining above 95%), increase MOD-SEVERE by one category
  • For dry snow conditions (Maximum temperature remains less than 26F), double the precipitation thresholds for MOD-EXTREME
CANL Criteria

The CANL system was created by the NOAA/National Weather Service in Glasgow, Montana; Dr. Larry Kalkstein at the University of Miami and Dr. Katrina Frank at the University of Delaware. Dr. Kalkstein is a leading researcher on weather effects on humans (biometeorology), and Dr. Frank has a background in animal sciences and climatology (bio-climatologist). The system is designed to indicate weather conditions dangerous to newborn livestock. The criteria for this system were derived from interviews with ranchers and from published scientific research on animal health.

We are targeting livestock that are less than 24 hours old because these animals are least able to regulate their body temperature and therefore most susceptible to the cold. Also, after several hours, producers may have had a chance to get to the animal, dry it off, and provide shelter as needed.

Detailed graphics will be available on the local office websites.

Feedback is appreciated. You can provide feedback or ask questions about the system by calling Tanja Fransen at the NWS Glasgow office at 406-228-2850, or emailing her at Your local WFO is available as well.

This system was developed by the University of Miami and the National Weather Service in Glasgow under a sub-award with the University Corporation for Atmospheric Research (UCAR) under Cooperative Agreement No. # S08-68874 with the National Oceanic and Atmospheric Administration (NOAA) and U.S. Department of Commerce.

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