Dark colors and dew point

Like one or two others I'm sure, I've had issues spraying in the spring and fall, especially with dark colors. I've got a job that we didn't finish last year that I'd like to get done here in the next few weeks as the weather's starting to improve. The problem is it's spraying gutters and some handrails in black.

In order to avoid problems that I've had in the past I'm going to be a bit more scientific this time, rather than just painting when it's warm and dry out and not too late in the day. Do I understand the dew point correctly that if the overnight temperatures don't drop below the dew point there will be no moisture on the substrate overnight? I'll be using Regal soft gloss. Thanks in advance.