In general, colder temps. are better. But what is concidered "cold" varies as much as terrain does across the country. Colder than average "for your region" in general means that coyotes need to eat more and eat more often, because their bodys burn calories just to stay warm, BUT that doesn't mean that they won't come when it's above average temps.
Precipitation isn't a deal killer. BUT heavy precip. isn't good. Light to moderate precip. won't hurt anything.
Just because they don't howl during the day doesn't mean that "howling" won't work to call them in during the day. Even out here in the west, they rarely howl much after sun rise, BUT they still come to howls because they are hard wired to respond to such things. They are territorial, and this is what you'll be triggering with howls. They most likely won't answer vocally, on rare occasions they will, BUT they will come to investigate the new coyote/s and possibly to guard their territoy, or pausably they may come looking for a pausable mate. In general, coyotes that come to "howling" come slower and more cautious, when compared to those that come for hunger reasons to distress. SO, I'd say if you're going to use howling on a stand, best get comfy and plan to sit 30 minutes, or even 45 minutes. And don't get caught with your pants down, because they could show up at any time in that period.
Recently I was in a contest in eastern KS. and the coyotes don't howl back there during the day time either, but we used a lot of vocals, on nearly every stand. Started with a few female invitation sounds nearly every stand, and on the one late evening stand that we had right at sun down, I even through in wolf howls along with the female invitiation sounds, and we had a pair come, the big male didn't leave the scene. We used no distress on that stand, howls only.