I live in a climate that gets even colder than your part of the world (if you can imagine that.)
If you're able to bury a cable then you might consider some sort of PVC conduit to place your wiring inside. To save money I usually by a roll of inexpensive PVC tubing and run ordinary Cat 5 Ethernet cable through it. While you're picking up the PVC tubing at your local home improvement store have a look in the electrical section at their PVC junction boxes and other fittings. You'll find all kinds of components to keep your cable and sensors dry and operating for years to come.
Don't forget to bury your conduit below the frost line, your local building department can tell you what depth that is and it's always a good idea to consider getting a line locate from your local utilities so you don't interfere with other underground services. I have low voltage cables running hundreds of meters to farm outbuildings using the method I've described and they have given reliable service for over 20 years.