A number of spots, mainly within higher elevations of western U.S. and parts of the far Northeast U.S., have already experienced an initial reading of 32 degrees (below).
But most parts of the nation have remained well above freezing — above the 50-degree mark.
Foliage is starting to turn color in some areas as indicated below.
The jet stream is forecast to become a lot wavier later this week with a dip in the jet stream over the west and a bulging north in the east.
This will result in unusual temperature anomalies — unusually cool over the western U.S. and unusually warm over the eastern half of the nation. This pattern will result in increasing odds for frost/freeze over parts of the Pacific Northwest and delayed arrival of frost over the central and eastern U.S.
Most livestock production regions are likely to experience above-normal readings stating late this week and persisting through most of next week.