Expected triple-digit temperatures this week spurred the first excessive-heat warning of the year for the Tucson area.

The National Weather Service in Tucson forecast high temperatures for Tuesday and Wednesday, June 6-7, of 105 to 109 degrees for the Tucson metro area, most of Pima County, and southeast Pinal County. Those high temperatures are about 7 to 9 degrees above normal for early June.

Conditions will be dry through Tuesday, but areas east of Tucson have a slight chance of thunderstorms Wednesday and Thursday. Temperatures will dip to normal levels later in the week and dry conditions will return.

The heat warning comes shortly after the Tucson area experienced the second-warmest spring on record, which included the warmest March on record.

The heat warning is part of the new HeatRisk forecast system the weather service is using this year. The color-coded system describes the level of heat risk, who is most vulnerable, how common the heat level is and how to address the risk.

The warning issued for this week in the Tucson area is red, the second-highest risk category.

That means high risk for most of the local population who are exposed to the sun, the temperatures are fairly common in the region, and residents should avoid being outdoors from late morning to late afternoon.

More information on the new system can be found at www.wrh.noaa.gov/wrh/heatrisk/

Contact reporter Curt Prendergast at 573-4224 or cprendergast@tucson.com or on Twitter @CurtTucsonStar