Over-wintered garlic & onions

Yes you can water them if it's that dry. Do a slow but thorough watering rather than tiny dribbles. Better to water well once than shallow many times over. I know several forum members are complaining of severe dryness while others are almost drowning.

The yellowing could also be a result of some frosting, but if soil is cracking, water regardless.

agree re:watering.

I also give them a gentle general sprinkling of FBB every few weeks or so during the growing season, too and get lovely large, juicy onion bulbs.