Sorry, couldn't copy and paste the frost penetration map. However, here is the text from above and below the mao.
Concrete Structures and Foundations
© 2002, American Railway Engineering and Maintenance-of-Way Association
8-3-6 AREMA Manual for Railway Engineering
3.2.4.3 Depth of Frost and Volume Change
a. The maximum depth of frost penetration shall be determined, usually on the basis of local experience
and records. Figure 8-3-2 is a map showing the depths of frost penetration in the contiguous 48 states.
Similarly, in regions of excessively swelling or shrinking soils, the depth to which significant volume
changes occur as a result of seasonal variations in moisture content shall be determined.
b. Permafrost, or permanently frozen ground, exists in the northern hemisphere in arctic and subarctic
regions. Although the southern boundary of permafrost is irregular, it may extend as far south as the
50th parallel. Foundations for structures, in areas of permafrost, should be designed in such a way as to
not disturb the permanently frozen ground; or if this is impossible, the influence of the foundation on
the permafrost should be predicted so the effect of the changes can be accommodated in the design. A
geotechnical engineer with experience in these ground conditions should be consulted for design of
foundations to be placed on permafrost.
Figure 8-3-2. Extreme Frost Penetration, in Inches, Based upon State Averages. Source:
U.S. National Weather Records Center