I'm not sure if you're doing spam approaching or semi-cold approach. Do you only talk to girls who will make eye contact, receptive body language, etc? If so, that's only semi-cold.
Whenever I'm in the mood, the situation is irrelevant so I guess you could say I mix it up
Pure spam approach where you just see a girl, chase her down and go for it, has very, very low success. The only credible numbers I've seen posted are about 1-100 for lays. And this was the best. It's common to find 1,000+ with 0 lays(that's actually the norm).
Which is why I'm pretty vehemently against spam approaching.

Semi-warm approaching, where she receptively meets eye contact or gives other signals, has a much, much higher rate. The best numbers I've seen are close to %5. Though the norm is probably about %1(possibly lower when starting out).

Warm approaching is where she's clearly into you. She's smiling at you, hovering around you, possibly even saying something to you, first. Success there, I've seen as high 1/3.
Hmm, seems like theres a flaw in your methodology or maybe I'm misinterpreting but even if a girl isn't a "warm approach" at first you can easily strike up a conversation with her and she'll be more into you afterwards. From my experience and knowledge it doesn't matter if shes into you at first or not, first impressions are great, sure, but ending impressions trump all. Correct me if I'm wrong.