While Chicago temps will have a mid-week rise in temps before a major cool-down by the weekend, a heat wave is building in Southern California and the U.S. Desert Southwest.

Heat Building in Southwest to Major and Extreme Risks

Southern California Heat Outlook

Experimental Heat Risk Map

The NWS HeatRisk is an experimental color-numeric-based index that provides a forecast risk of heat-related impacts to occur over a 24-hour period.

HeatRisk takes into consideration:

• How unusual the heat is for the time of the year
• The duration of the heat including both daytime and nighttime temperatures
• If those temperatures pose an elevated risk of heat-related impacts based on data from the CDC

This index is supplementary to official NWS heat products and is meant to provide risk guidance for those decision-makers and heat-sensitive populations who need to take action at levels that may be below current NWS heat product levels:

Courtesy National Weather Service