* WHAT...Heat index values up to 103.

* WHERE...Portions of northwestern and southwestern South Dakota and northeast Wyoming.

* WHEN...Until 8 PM MDT Sunday.

* IMPACTS...Hot temperatures and high humidity may cause heat illnesses.

* WHAT...For the Extreme Heat Warning, dangerously hot conditions with heat index values up to 116. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 110 possible.

* WHERE...In Iowa, Fremont, Harrison, Mills, Montgomery, Page, Pottawattamie, and Shelby Counties. In Nebraska, Douglas and Sarpy Counties.

* WHEN...For the first Extreme Heat Warning and second Extreme Heat Warning, until 9 PM CDT Sunday. For the Extreme Heat Watch, from Sunday evening through Monday evening.

* IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events.

* WHAT...For the Extreme Heat Warning, dangerously hot conditions with heat index values up to 116. For the Extreme Heat Watch, dangerously hot conditions with heat index values up to 110 possible.

* WHERE...In Iowa, Fremont, Harrison, Mills, Montgomery, Page, Pottawattamie, and Shelby Counties. In Nebraska, Douglas and Sarpy Counties.

* WHEN...For the first Extreme Heat Warning and second Extreme Heat Warning, until 9 PM CDT Sunday. For the Extreme Heat Watch, from Sunday evening through Monday evening.

* IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events.

* WHAT...High temperatures of 100 to 104 expected Sunday.

* WHERE...Fort Collins, Boulder, Denver metro, and Greeley.

* WHEN...From 10 AM to 9 PM MDT Sunday.

* IMPACTS...Hot temperatures may cause heat illnesses.

* WHAT...Long-period southerly swell will bring an increased risk of sneaker waves and strong rip currents. Breaking waves will reach up to 10 feet along some south and southwest facing beaches and break points.

* WHERE...Beaches along the Pacific Coast.

* WHEN...Through Wednesday afternoon.

* IMPACTS...Dangerous conditions are forecast along the shoreline. Hazards include sneaker waves, strong rip currents, and large breaking waves.

* ADDITIONAL DETAILS...This swell is being generated by tropical cyclones in the Eastern Pacific.