What is warm to some people may be hot to some and cool to others; when some people are a bit cold, you may still find it warm.
There is no rule that says "X degrees is warm" but "X+Y degrees is hot."
To my thinking, if you can go out in short sleeves and be comfortable, it's warm. If you go out and wish you were back in the air conditioning inside, it's hot. You can create your own rule -- if you need to put on your air conditioning to be comfortable, it's hot, for example.
However, to answer your question, if you are sweating while standing still, it's definitely hot out!
(You can sweat even in cold weather if you are working hard, though.)