There are exceptions,because of individual environmental circumstances,but the low temperatures of your area are about the limit. Some people successfully grow them, in the ground, in colder areas.Some of the contributing factors to that success are deep burial,heavy mulch,being close to a building foundation of a heated building.Being planted on the south or west side of a house can help.
Some varieties tolerate cold better than others.Very few tolerate very cold and heavy moisture.Red Lion is said to be cold resistant. Some Hippeastrum species come from high altitude areas of south America, Those and their hybrid progeny are more likely to be cold resistant.
The larger bulb a hybrid has,the more likely its survival,because of it's self insulation.
Hello, I am in Texas, zone 8A, i have had Hippeastrum x johnsonii for 11 years and they were planted before i moved here...they have prolificated like crazy ...i move them around every couple of years. No problems at all with them. As for the other varities, i am unsure, but have purchased 15 new varities and i am hoping they are just as hardy. I plan to take one of each bulb indoors this winter, just in case.
I was surprised to see amaryllis at a nearby friend's house recently. She has what I believe to be Red Lion and Johnsonii. They are planted next to an unheated garage on a side facing the SE. We're officialy zone 7a, but I believe more like 7b. These have been growing for 10+ years.
I gathered the seed pods and will try to grow them.