I live in what is locally called the "Beemerville Basin". It is a glacier gouged basin about 1 mile across and 2 miles long, 200 feet deep with 65 acre swamp at the bottom. In winter when temperatures drop and snow covers the ground the temperature here is much lower than even a half mile away. Since last Sunday's big snow the thermometer on the north side of my barn has not risen above 0 at any time of day. This morning it was -15. At my friend Bruce's house about 1 mile away (not in the basin) he had a low of 1 degree. So the difference in temperature within 1 mile was 16 degrees. With the local temperature forecast it may not get above 0 by my barn for 10 more days. This temperature thing only happens when we have a lot of snow on the ground and very cold temps. Has to do with the construction of the "basin" and the fact that cold air sinks below warmer air. Also makes it windy, night and day. Today, this morning, my barn was 35 degrees colder than Anchorage, and 17 degrees colder than Fairbanks.

I grew up in the Des Moines River valley and remember kind of the same thing. Colder at the bottom of the valley as the cold air settled in. But it was usually less windy as the wind seemed to just blow over the top of the valley.

Interesting.....

We have an area of dwarf pine barrens a few miles away that is always colder than the surrounding areas. If we get single diget temps in our area, it will be zero or below there....
Never heard of an explanation why....

I used to have the reverse of that living on a big shallow black bottomed south facing slough of the warrior river. The ridge a hundred foot above me would be 5 to ten degrees cooler and be frosted while I almost never got frost in my yard on the river bank. That slough was a giant heat sink.

I got one I call it the frost pocket.