Post-fixing or pre-fixing "mind you" onto an informative/descriptive statement

Example:

It was quite a sunny day, mind you.

or in the middle:

It was quite a sunny day, mind you, so I packed my sunglasses.

or prefixed:

Now mind you, it was quite a sunny day...

What is meant to be conveyed? That I should be mindful of the fact that was stated? I can understand that much, but somehow it doesn't quite fit in with my understanding of the word "mind" when used in other contexts: "Do you mind if I borrow your car?" or as a verb: "Mind the gap." (at subway stations between the train and platform).

Can someone break it down?

Solution 1:

The core meaning of the verb mind is ‘remember, bear in mind’. When used parenthetically, usually in speech, mind, with or without you, serves as an imperative to add force to what is being said, or even to express a degree of contrast with what has gone before.

Such expressions are best seen in some kind of context. The speech you give as an example would not occur in isolation. It might, for example, be preceded by I didn’t really want to go. It was a long way and I didn’t know the other people. When that is followed by It was quite a sunny day, mind you, so I packed my sunglasses, the speaker says that he had reservations about going, but asks the listener to bear in mind that it was nevertheless a sunny day and that he therefore overcame his reservations to the extent that he packed his sunglasses.