If you can pick your days to rattle, know that dew is good. Moist grass and high humidity helps to soften footsteps and cover scents. Of course this also means you can't hear approaching deer as well. As always, step over downed branches during your hike into position and hope that deer don't do the same. Fog is good, too.
Overcast skies help to eliminate a deer's sight distance.
Of course, again, you can't see as well either on a gray day. Rattling is usually good following extreme weather, when animal movement has been restricted. Coordinating your trip with a herd's sexual activity is the key to consistent success. It's then when bucks looking for a fight are anything but subtle. This is mostly evident a few days into the rut or toward the end, when does are still hot and many already have bred.