Elk City is Z5 - but that's not really a good indication of growing capabilities based on winter temps. It has springs that correspond closer to Z6.

Here is a link that might be of interest - scroll down to the temp charts.

Here is a link that might be useful: Elk City

I would guess that Elk City is in zone 4. You can verify this if you can find the right weather statistics. Zone 4 means that the average annual minimum is -20 to -30 F. You can calculate this number by finding the temperature on the one coldest day of each year and averaging that over many years. It has nothing to do with spring temperature. I have a book called Climates of Idaho which has information from Elk City reported from the Ranger Station, but does not give the exact numbers I was looking for. It does mention that 2 of 10 winters have a low below -29. That is based on the average from 1961-1990. It may not be that cold now.

They've already had frost there.

Thanks every one, I guess I'll need a conservatory AND a green house! Well there are other things I can enjoy growing, I've never been much of a veggie gardener anyway!

There are lots of great cold-climate prennials that should do well in that area. Sometimes you can even push the zones if you have a good reliable snow cover in the winter.

Yeah, I remember when we moved up here 20 years ago, I was told I wouldn't be able to grow alot of things. The elevation is 3300 ft and we're in zone 7 and there've been quite a few things I've been able to grow well that the local garden centers said I couldn't. There are always things to consider like south facing slopes,etc.