The record low at the National Weather Service (NWS) near Negaunee today is 43 degrees set back in 1988. This is the warmest record low in the books at this site, which means we are truly at the height of summer. The ground is nearly at its warmest and Lake Superior has warmed greatly over the last few weeks (Image 1 above). Even to the north, Hudson Bay has lost much of its ice (Image 2). Yes, believe it or not, there is still ice up there. It is not at all unusual. The Bay usually keeps at least some ice into August.
What this means is that cool air masses do not have nearly the bite they did just a few weeks ago. While nights are getting longer by a minute or so every day, the above factors mean things just don??t cool off that much at night at this time of the year. Interestingly, there are two other days with 43 for a record low and these both fall within the next week. Afterwards, there are a couple of days with 41 or 42 and then a number of ??mild?? 40-degree record lows into early August. However, once past August 9, all record lows are in the 30s. The lengthening nights eventually allow the earth to cool, which leads to opportunities for chilly overnight lows if the conditions are right.
There will be no chance of cool nights over the next several days. We have locked into a real summertime pattern. Nights will be warm, but not unbearable, through the weekend. That??s because a huge upper-level ridge is building in. This ridge will lock in a dome of warm air which should linger well into next week. One caveat with this air mass should be a tolerable level of humidity which will mean nights should be mild, not stifling.