I apologize for my slow response . . . between my ability to miss seeing some posts, and a really busy day yesterday in which my "major accomplishment" was coming down with some kind of virus, well, I missed it.
So.
I live in New England. Does that count?
Depending on how well you are set up to brood the ducklings, you may be okay to start, or you may want to wait. Due to a miscommunication, the runners I ordered for 3/23 delivery arrive on 2/23. !!! This was not a huge problem because I had converted our guest room to what I called The Brüderhaus. (Strange sense of humor, I know). Anyway, that meant that it was easy to keep my baby-duckies warm enough, dry enough, safe enough, etc.
That year, spring came very, very late. Very late. We had indoor ducks for three months. My inner nine year old was delighted. And we had absolutely no odor problems. I had the luxury of being a SAHDM, so I could keep up with cleaning the brooder.
While there is a wide variety of experience in this regard, Storey's Guide to Raising Ducks recommends brooder temperature of 90F the first week, dropping 5 degrees F per week until the ducks are feathered and the outdoor temperatures line up with the ducks' healthy temperatures. There is variability here depending on duck breed, individual ducks' constitution (Fünf and Sieben are my least cold-hardy ducks). Since I had nothing to prove, and no problem keeping them in until nighttime temperatures were above 40F, they stayed indoors at least at night for that three months.
They did start getting outside during the day from about six weeks of age. Days were pretty nice and warm. Nights, however, were very cold.
Here is something I have noticed about new duck owners. Many are surprised and appalled that ducklings splash so much. They splash their water, their feed, their poop, in our case, they splashed the soil from a potted plant one night (long story) all over the room. And if the cleanup schedule does not keep up with the splashing, there develops a distinct and unpleasant odor.
That is the point at which we see threads asking when they can get their stinky ducklings outdoors. I feel for the people and the ducks. But I tend to side with the ducks. Yup. Unfair, but true.
So, again.
If you have accommodations that will keep the ducklings warm enough and dry enough and safe enough, even if there is an unusually cold snap of weather, go for it.