Leaving work at lunchtime, I saw a couple of sulfur butterflies spiraling in a courtship pattern, and a third flying nearby. It was close to 70°F this afternoon, warm and sunny.
Here's a cloudless sulfur taken by Gene Hanson in Arizona. He has a great site with beautiful butterfly images (he was gracious enough to let me use several for one of the Garden's butterfly garden signs).
We have a number of sulfur species; they have great common names such as Clouded Sulphur, Little Yellow, and Cloudless Sulphur, and Southern Dogface. It may have been something like a Little Yellow that I saw, since they had dark-edged wings. But I didn't have time to really get a good look at their markings. Many sulfurs specialize on different legumes for their larval host plants, while a few focus on blueberries and willows.