I'm not sure this is so simple. Clearly your answer is correct with a largely uninsulated house with a basement only partially below ground (perhaps most of the developing world to be fair). Any semi-sealed home will have heat naturally accumulate (and dissipate) at the top. Apparently the movement of air upward - known as the stack effect - creates a (slight) vacuum pull at the bottom. Of course it's a small effect in normal temperatures but in extreme reverse stack-effect scenarios like you're describing the ground temperature below 3 - 5 feet should result in a basement being lower temperature than the backyard as available air gets sucked through the cooler ground to get into the basement? I'm sure this varies widely by region (ground temps vary in 3 - 5 ft depths) but everywhere this temperature will be cooler than the outside in such weather extremes.