How can we have frost at my house when the freezing level is higher than our elevation?
The key here is to realize the freezing level reflects temperatures (expected or actual) in the 'free' atmosphere...not affected by the ground. Temperatures at the surface (such as near your home) ARE affected by the ground. Rock, pavement, etc all absorb or radiate (lose) heat at different rates...and can cool much faster than air which isn't in contact with the ground. Additionally, because cool air is more dense than warmer air, it will drain downslope, and collect in low spots, such as valleys...which can also give such areas much colder temperatures (and frost) than surrounding areas.