Check the websites below:

Azaleas and Rhododendrons for Minnesota

Azaleas and Rhododendrons for Missouri

The most difficult to grow are evergreen azaleas. Most are not cold hardy. Deciduous azaleas and evergreen rhododendrons are very cold hardy and many cold hardy plants are also heat hardy. The "PJM" rhododendrons are small leaved rhododendrons similar to azaleas in some ways, but are extremely hardy. There is also a series of rhododendrons and azaleas from Finland:

Finnish Rhododendrons

Here is a link that might be useful: How to Grow Rhododendrons and Azaleas

We can grow girard azaleas here. They come in a variety of colors and are evergreen.

I am trying out a few rhodies this year.. will let you know how that goes...

So far, the azaleas have done very well for me, and I hope they continue to as I have about 21 of them now!

I have PJM in Chicago area. They are doing great. Give um a try. They look awesome when they bloom in the Spring.

The problem with some PJMs is that they bloom so early that a late frost comes along and freezes the buds or flowers and kills them. To avoid this choose members of the PJM family that bloom later such as:

Bluenose: similar to PJM but blooms in mid season
Landmark: almost red PJM but blooms in mid season

The pjm does bloom very early. I have an unnamed one that I bought for a nice price last year (in a 3 gallon pot for $2.50 cuz it lost it's tag!)it bloomed WAY before any of the others, including azaleas. You can watch it, and if we are to get a late freeze or frost, you can cover them with something for the night like my mom does her cherry bushes.