Yes, and no. Do you have any reason to think that your digital thermometer is accurate? Your only options, as already discussed are to get an accurate thermometer to calibrate against, or use some other known temp e.g. freezing & boiling (adjusted for altitude) water. Having said that, for your purposes, does it actually matter if your measurements are a degree or two off? For minimizing power consumption of course, perhaps it does.
It's the classic problem of telling time with two watches - how do you know if either is right?