A broad upper ridge has moved into the central US. As a result, very warm air has moved into the Northern Plains, along with relatively high humidity with dewpoints in the 60s to near 70 degrees. Heat index values are expected to remain in the 90s and may occasionally top 100 degrees during the afternoons through Sunday. This amount of heat and humidity is early for the summer season, with highs expected some 15 to 20 degrees above average. Even more unusual is that the heat will persist for 4 or more days, and some nighttime temperatures may not drop below 70 degrees... especially on Saturday night. Below are forecast high temperatures.

A Heat Advisory is in effect until Saturday evening for areas shown below. This means heat index values may exceed 100 degrees at times.

Aberdeen reached 100 degrees for the first time since July 19th, 2011 Thursday. This also tied a daily record high temperature (1933). Moving forward, widespread records are not expected, but some locations will continue to be in record territory.

Many people don't realize how quickly vehicles can heat up in the sun. Leaving the windows slightly open does not significantly decrease the heating rate. The effects are more severe on children because their bodies warm at a faster rate than adults. A dark dashboard or carseat can quickly reach temperatures in the range of 180 to over 200 degrees F. Never leave a child unattended in a vehicle on hot days, even just for a minute. Just remember, Look Before You Lock!

It's also important to keep in mind that simple air temperature is only half of the equation. When humidity is factored in, it can feel downright oppresive. Worse, your body is less efficient at cooling itself in high humidity environments. As a result, heat-related illnesses become more likely. Below is the Heat Index chart.

Although this likely won't be an extreme heat event, it'll be the first real heat wave of the year. Therefore, it's important to remember some basic tips if spending prolonged time outdoors to prevent heat-related illness (common heat related illness information: http://www.nws.noaa.gov/om/heat/heat-illness.shtml):

• Drink water often
• Rest and cool down in the shade
• Know symptoms, prevention, and emergency response to prevent heat-related illness and death
• Check weather forecasts ahead of time to be better prepared

For more information, visit http://www.nws.noaa.gov/om/heat/index.shtml