How does soil temp correlate to air temperature?

[JerryHaskins]

I am not sure if this has been discussed already, if so, please point me to it.

I found this great table showing the effect of soil temperature on seed germination:

http://tomclothier.hort.net/page11.html

And I have one of those little soil temperature measuring instruments.

But does anybody know how soil temperature relates to daily maximum and nightly low temperatures.

Obviously, it matters how long it's warm or cool during the 24-hour period, whether it is cloudy or sunny, how much it rains, the hours of daylight, amount of mulch, etc.

But daily weather forecasts on TV and the internet give the minimum and maximum air temperatures. That's easier to find than soil temperature.

I just wonder if anybody has tried to correlate air temperature to soil temperature.