Place the potato chunks in a large pot and cover with cold water by about an inch. Bring to a boil over high heat, then reduce to a simmer and cook for 12-15 minutes until just tender when pierced with a fork.
While the potatoes cook, make the dressing by whisking together mayonnaise, sour cream, dill, Dijon mustard, and red wine vinegar in a medium bowl until smooth and creamy.
Drain the cooked potatoes well and transfer them to a large mixing bowl. Let them cool for about 5 minutes—they should still be warm but not hot.
Add the chopped celery and red onion to the warm potatoes, then pour the dressing over everything. Gently fold until the potatoes are evenly coated.
Season with salt and pepper, tasting and adjusting as needed. Remember the flavors will develop as it chills.
Cover the bowl and refrigerate for at least 1 hour before serving to allow the flavors to meld and the salad to chill thoroughly.