If you can get a spotlight that is about 100K to 200K candlepower with a red lens, that would be idea. They keep making spotlights brighter and brighter (some are at 2m CP), and you really don't need one that bright.

I do most of my calling during the daytime because its easier to see and shoot without trying to hold a gun and a spotlight on the coyote at the same time. If you sound distressed enough, they will come to you whether it's 10 degrees or 110 degrees outside.