I have not tried an inground or even partially buried bin, but I can still point out some inherent problems. The first is what do you plan to do with any castings produced? If you are composting pet crap or even human feces the you would probably fix things to actually flush the composted material into the soil deep down.

However if your intention is to process household garbage into a usable product for your houseplants or garden then I would recommend a system where you can retrieve the castings. Almost standing on one;s head to dig out castings is NOT my idea of efficiency. the older I get the more it appears to be torture.

While the soil temp wold be alot more stable that the air temp, I would recommend you move your endeavor indoors. You can keep worms without any smell. In fact my wife was not even aware I was keeping a few bins in a spare bedroom we use mainly for storage until she went in to look for a suitcase.

I have similar temperatures and have 3 different types of worm setups. I use a large rubbermaid bin in a shady place that finishes my cold compost. I put frozen water bottles on top of leaf bedding, leave the lid slightly open and they do just fine. I have also kept worms in 8" washtubs. I have another bed, (kinda like a flower bed) under a shade tree that I feed excess food weekly. I cover it with 2-3 inches of brown leaves and sprinkle with the hose daily. There is also my raised square foot garden with numerous worms and many pots with worms. These don't have any covering but are kept damp. What kind of problems are you having? Hope some of this helps.
Kath

In the hot Australian summer, I just make sure the bins are in the shade, then remove the lids and cover with hessian or similar which I keep damp. The evaporation then keeps the bins cool. Simple!

My worm pits are in mottled shade from Eucalyptus, covered with carpet scraps, sprinkled daily with hose. These worm pits multiply rapidly. When I prep to harvest VC, I lure worms with something irresistable like watermelon rind or pumkin and put the greedy worms in a 'holding bin'. Then dig and sift out non-greedy worms who are also put in 'holding bin'. When done harvesting VC, place new bedding [horse/steer manure]in harvested space and repopulate with worms from the holding bin. I do this 2 or 3 times a year.

BTW ... in addition to hot summer temps, what are your winter lows?

Here is a link that might be useful: Hi-Lo temps by state