A Wind Chill Advisory is in effect for much of northern Iowa this morning as cold air and brisk winds are coming to push feels like temperatures well below zero. The featured map displays the yearly frequency of Wind Chill Advisories by county in the state. The highest frequencies are shown over the flat areas of north central Iowa with Fremont County in far southwestern Iowa indicated as the lowest. Why does such a gradient exist over the state? The coldest air masses arrive in Iowa from the NW and the flat areas over north central Iowa are the windiest in the state, so this area is favored for the coldest wind chill values. Also as you go south and when winds are from the NW, these tend to be more chinook influenced, which means the air is warmer due to down-sloping from the Rocky Mountains.

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