During the winter, not more than a couple of inches, depending on where you live. Along the coast, it's less; in the mountains, it may be higher.
In the summer, there is no frost line.
4 feet
no Frost
Up to July 2008 it was 4' per the NYC Code. I haven't dealt enough with the newly adopted code. I imagine it hasn't changed.
Average is 4ft, building code requires water pipes to be at least 6ft deep to be well below frost line and safe from frezzing.
no Frost
The frost line in Springfield, MO is typically around 30 inches. This is the depth at which the ground is expected to freeze during the winter months. It's important for construction and landscaping to prevent frost heaving.
I found this link...I hope it helps. From what I can discern the frost line is at 42" http://www.ci.omaha.ne.us/planning/building_development/Code%20Info%20Sheet%203-06.pdf
i dont know whho cares Most concrete foundations are buried 4' to get below the frost line which is around 3'.
one metre
42"
42 inches
3ft