I had always thought you were in Zone 4, Ro, but when I consult my most detailed copy of the USDA Hardiness Zone map (which I got in an old issue of Fine Gardening) I see you actually are listed as Zone 5. Not that the map is the last word on what zone you are. When we first moved here in 1989, we had at least a week of winter lows to minus 30 degrees Fahrenheit. In 1993 it got even lower. But somewhere along the line, the winters started getting warmer. It’s gotten to the point where I’m surprised when we get subzero temperatures.
So, were those cold temperatures just a fluke, or are these warmer winters a fluke? Who knows? Maybe they’re both normal for this area. I still consider my little locale Zone 4 because the growing season is still Zone 4 short. Our last spring frost can still often be the first week of June. Rose, I think you had your basil planted out way before that! And while our first fall frost seems to be getting later (mid-October), when it comes, there’s no pussy-footing around: it’s a hard frost right from the get-go. That’s why I consider my garden Zone 4, even though, strictly speaking, it hasn’t had a Zone 4 winter in several years. But I have to confess, I’m a little more willing to try plants labeled Zone 5 than I used to be. Of course, a lot depends on the plant. This past winter I had snapdragons that wintered over, but still lost my foxgloves to the combination of HOT April weather that brought them out of dormancy followed by FRIGID May weather that froze them solid. Supposedly the foxgloves are more cold hardy than the snapdragons, but the snaps had a better coping strategy this year, at least.
There is simply no substitute for an intimate knowledge of one’s gardening site, part of which comes from observing and recording the weather, day by day, year by year.