Excessive Heat Warning

WEDNESDAY-LABOR DAY : Significant long duration heat wave likely away from the immediate coast

Ventura County, CA: The National Weather Service is forecasting a prolonged period of high temperatures that is expected to impact Ventura County over the next week. In some areas, these temperatures are expected to be record-setting, with poor overnight recovery. Additional information related to this heat event can be found in the attached PowerPoint presentation and on the National Weather Service website here.

Operational Area Preparedness

  • Ventura County Public Health will be issuing a press release with details on heat-related emergencies.
  • Information on cooling centers has been added to VCEmergency.com in English and Spanish
  • Although there will be an increased threat of wildfires, no red flag warnings have been issued by the National Weather Service due the lack of wind with this event. 
  • No threat of public safety power shutoffs by Southern California Edison
  • No current advisory indicating the potential for rolling blackouts.
  • Although Cal ISO is indicating all available power sources are being brought online, a Flex Alert will likely be issued for peak temperature days. 
  • The Ventura County EOC will be remaining at Duty Officer level.
  • The Ventura County Fire Department will not be going into a “Plan 1 Heat” or “Plan 1 Bruch” unless the forecast or situation dictates otherwise.



Temperatures:  o Coastal Plain: Max 76-96, except 90-105 possible on Sunday and Labor Day o Valleys, Foothills, Lower Mountains, Deserts: Max 97-110, except 100-115 possible on Sunday (Warmest Antelope Valley, San Fernando/Santa Clarita Valleys, San Luis Obispo Interior Valleys)  o Hot sundowner wind event Wednesday evening will likely keep temperatures in 90-100 degree range across foothills/wind prone canyons of Santa Barbara South Coasto Wednesday will be very warm across entire area with some slight cooling Thursday and Friday, especially across the coastal plain and coastal valleyso Heat will intensify again Sunday and Monday for all areaso Mixing heights 10,000-18,000 feet across interior sections each afternoono min 72-85 each night across valleys, foothills/lower mountains·  

Humidity o Minimum 8-20% § Humidity levels falling to 15-25% for sundowner event Wednesday evening (foothills/wind prone canyons)§ Some uncertainty in humidity levels across LA/Ventura counties by Sunday/Monday due to potential influx of mid level monsoonal moistureo Poor overnight recoveries, especially foothills/mountains·  

Winds o Typical onshore sea-breezes in afternoon/evening for most areaso Except northwest-north winds gusting 30-50mph Wednesday night across western portions of Santa Ynez range and adjacent foothills/canyons and I-5 corridor§ Strongest sundowner winds near Gaviota/Refugio§ Peak SBA-SMX gradient -4 to -4.5 mb Wednesday evening·  


  • Elevated to brief critical fire weather conditionsall areas away from immediate coast due to extended heat wave with low humidities 
  • Gusty northwest to north winds Wednesday night across I-5 corridor and western portions of Santa Barbara south coast/Santa Ynez mountains will bring greatest chance of brief critical conditions (1-3 hours Red Flag conditions possible) 
  • Many portions of SW California now have critically dry fuel moisture levels, bringing increased risk of large fire growth with upcoming heat waveo Some uncertainty with Sunday/Monday time frame
  • Potential weak offshore flow could generate very hot temperatures
  • Potential influx of mid level monsoon moisture/instability across LA/Ventura counties may impact temperature/humidity forecasts (10 percent chance of elevated thunderstorms) 
  • Potential for large vertical plume growth for any new fires away from the coast due to  hot/unstable conditions 
  • Similar long duration heat waves generated large plume dominated fires in late August/early September (i.e. Station/Bobcat fires)