I live in far northern Wyoming and have grown every kind of tomato imaginable. I start them 8 weeks before setting out on May 15. I use milk cartons to protect them until June. Bitterroot Valley (are we talking Libby? Kalispell?) gets a whole lot of snow whereas I get almost none all winter (have none now) My growing season is anywhere from 90 to 150 days. Just never know. I have never limited my choices based on early, intermediate or late...I have had equal success with types from all three. I would advise protecting young transplants from the wind (We get a lot and I know Montana does as well) I have had wind literally kill young transplants by stripping them of all their leaves and drying the plant out (and I mean the plant on the top of the ground) to the point where it withers from the evapotranspiration. If they don't die, they are set back so much it's barely worth letting them grow out. I put bales of straw behind my plants facing the direction of prevalent winds. The straw also retains and reflects heat and the plants do better in early season cooler weather. Perhaps growers in Michigan, Wisconsin, The Dakotas, etc could be more helpful as their climate is more like yours as you will be living so far north.

You stated:"I put bales of straw behind my plants facing the direction of prevalent winds." I'm confused, is the bale between the wind and the plant or vise-a-versa?

Sorry, I even thought about how to write that sentence and it still did not come out right! Between the wind and the plant. All of our wind comes from the Northwest. Poor little young plants just can't take that howling stuff. I don't mind toting straw bales as barley is pretty light (2 wire bales) I set them all in a stack after I am done with them and then they are ready to do duty again the next year.
(after about 3-4 years the baling twine starts to rot so I rotate those bales into my mulch material.) Oat straw is heavier but we don't get much of that available here. Old rotten/moldy alfalfa is REALLY heavy and "PEEE EEEWWWW". I do grind bad bales up in my chipper/shredder to rototill the soil but it is a stinky yucky job. The protein is really good in ALfalfa (a legume) so it is a good soil amendement but IMHO it needs to be ground up or it is slow to compost.

Here in southern NM the wind really blows March thru April, our planting time. My garden is over a rise and pretty much protected. Because of the high summer heat/sun, I shade the garden and plant an early and late garden. Flower pollen becomes stick above 90 F which is most of July and August, not good for tomatoes and the like.

You might want to take a look at the Seeds Trust High Altitude Gardens site.

Here is a link that might be useful: seedstrust

Also, I haven't seen anyone mention growing it, but this is one of the offerings from Sand Hill this year:

Imur Prior Beta: early, Ind, PL, 2 to 4 oz. fruits, high yields, taste on the sweet side, bred in Norway for short season areas and high altitudes.

You might drop in the Rocky Mountain Gardening forum here at GW. We have several hardcore mater growers from the entire mountain states area. Several threads over there about tomatoes that do well and don't do well.

Imur Prior Beta yup. Grown it. Got it from Spudleafwillie. :D

Here is a link that might be useful: Rocky Mt. Gardening

For the wind, 5 gallon buckets and a rock on top of the bucket. No way would I have any tomatoes if I did not but them on and off. Wall of water works pretty good, but I
have had then blow over too.
Kenny in NE Colorado

jalirancher...thanks for the link. A big well-duh! lightbulb went off for me when I saw it. Of COURSE Rocky Mountain gardeners have to deal with similar conditions to ours in in the spring in the high desert: warm days, cool nights, harsh winds, and always the possibility of a late frost.

Trotting right over there now....

Jan

To go along with what jaliranchr had to say, you might also consider a hoop house. I am north of Denver and start my peppers and tomatoes in mid-Jan or early Feb. After potting up to 4" square pots, I plant out in the hoop house (usually around early April). Yes, it can still get pretty cold so I have a small 1500W space heater out there with a couple of small fans to circulate the air.

When the weather finally warms up, I start opening the ends of the hoop house to keep everything from cooking. I still have to close it at night. Usually about mid-June, I take the plastic off and start putting cages on the tomatoes (if I haven't already).

Yes, it takes 4 months of preparation, but it is worth while. Everything has a good start, most have already tried to bloom at least once or twice, and they are all sturdy and healthy plants.

Good luck!

--->Rob

when I move I am buying a 12x36 ft greenhouse for starting seedlings and growing some inside and some outside with hoop protection when the freek weather hits - can snow in Jul or Aug - more interested in varieties that do well in this area