Well, spring is here, but it always seems like it takes a while to shake that lingering winter chill. And this time of the year, landscapers and home gardeners are all wondering when that final freeze will occur so the growing season can officially begin. As seen on the map below, the Midwest typically dips down to the freezing mark for the last time in late April. Indianapolis, Indiana is usually the earliest to observe its final freeze, while Rockford, Illinois is still susceptible to damaging cold until the end of the month. It's important to keep in mind that even if the air temperature is above freezing, clear and calm spring nights could still pose a threat to vulnerable vegetation. If the ground radiates enough energy, temperatures near the surface could fall to freezing, if not a few degrees below. That's why frost develops on plants some mornings, even if overnight lows only fall into the mid 30s.
Of course, the dates above are just an average based on climatology. To gain a better idea of the date range that the final freeze can be observed, see the chart below. It lists the all-time latest final freeze dates at each of these major Midwest cities.
