Excessive Heat Warning criteria

As we go through today, if you aren’t under an Excessive Heat Warning, you are under an Excessive Heat Advisory. The counties under a Warning today will be Berrien, Cass, LaPorte, St. Joseph, Elkhart, Starke, Marshall, Pulaski, Fulton, and Kosciusko. This means the NWS is expecting maximum heat index values above 105 degrees, as well as a minimum heat index value of 75 degrees for a 48-hour period. Remember that heat index is the combination of temperature and humidity, so a 75-degree minimum has been very easy to reach when our normal lows are barely dropping below that. In an advisory, you are still expecting to see heat index values nearing 100 degrees, and/or a high temperature of 95 degrees.

Once again, the criteria for an excessive heat warning in Northern Indiana is very lofty to reach, a heat index above 105 and a minimum of 75 over a 48-hour period. All of the heat waves that we have seen haven’t gone above 94 degrees, and with an expected high of 98 in South Bend, it is definitely going to be easier to hit a triple digit heat index. South Bend doesn’t regularly see temperatures in the upper 90s, and there is only around a 15% chance that you would see heat index values above 105 degrees this late in August.