On average, March and April are arguably better months to thru-hike than April and May. Just in terms of probabilities, you’re more likely to find water, less likely to be dealing with wildfires, less likely to be walking through intense heat. You’re more likely to encounter snow in the high country, and especially on the north rim of GC. But the associated challenges are typically fleeting in comparison with walking through the desert in May of a drought year.
Garlic is spot on, though. “On average” doesn’t mean much, especially of late. If you can, you’re better off remaining flexible, waiting to see how conditions look toward the end of winter. With its extreme range of terrain and elevation, there’s no such thing as an all-around ideal time to thru-hike the AZT. But you’ll be much more likely to dial in a schedule that’ll work best for you by simply waiting and seeing what unfolds between now and next spring.
blisterfree