Mine would be a toss up between Falkreath and The Reach, Falkreath because it is almost always misty and raining and that is more than perfect for my adventures in its beautiful forest. I feel a great sense of wonder exploring the forests of Falkreath, it also feels a lot like Cyrodiil to me which is appreciated. Falkreath is also a very mysterious and dark place which adds to its beauty; and The Reach because it is stunningly green, the mountains provide an incredible backdrop and the fog over its rivers and lakes is quite a site to admire while riding through the hills. Also, Markarth is a very intriguing city to me due to its Dwemer history. The people in these holds seem quite welcoming to outsiders as well which helps =)
What's your favourite hold?

anything over 60 degrees is to warm.
and still has a decent number of inhabitants!