Welcome to the forum. You have a very exciting scenario and I would love to have your problem! One station that you should give serious consideration is the Davis Vantage Pro 2. They have numerous models that range in price from $600 to $1200 USD. You will probably want to lean toward the higher end. You will also require a data logger (which comes with the Weatherlink software) which costs about $165 USD. This will get your data on a PC. I bought mine from Ambient Weather a couple years ago and if I recall correctly shipping was in the $60 ballpark and customs into Canada another $70 for the $1200 unit. I operate mine in Ontario and it has no problems in this climate. Our coldest winter weather is closer to -25C but the unit is rated to -40C. The VP2 will do a good job with temperature, wind speed, wind direction, humidity, pressure, rainfall, solar, and UV.
One challenge you will have is measuring snow. The VP2 comes with a rain bucket. You can search the posts for adding heaters to the bucket but even if you did, at -40C I am sure you would have freezing problems in the tipping buckets below. Add a little wind and the snow won't even collect in the bucket. Sadly a yard stick from Canadian Tire might be as accurate.
The software calculates evapotranspiration which may be of interest to you. I believe you need to get the solar and UV sensors for this parameter.
The wireless VP2 unit has a range of about 300m. I run mine about 200m and then into my house without problem. It is interesting to note that Davis sells wireless and solar repeaters with a Yagi antenna. I was just looking at their brochure and each yagi has a gain of 10dB. So the range is about 3 km or 1.9 miles. They claim to have successfully tested it with two Yagis for a total distance of about 4 miles. Maybe you could transmit all three stations to one site? However, I expect 3 PCs would be more reliable.
You could use the standard Weatherlink software to collect the data and upload to the net. However, there are lots of other popular options. VWS, Weather Display, Cumulus, to name a few. I don't have any experience with collecting data from 3 complete stations and I don't know which software would work for that. Hopefully someone else will step up with that answer.
Lastly, I suggest you call Davis and/or Ambient Weather and layout your problem and hear what they have to recommend. Good luck and please keep us informed on your progress.
Dale