It may depend on how you planted them and your soils. Mine are doing great and could probably go for a few more weeks of drought with no issue. When you do traditional tillage you lose a lot of soil moisture. I surface broadcast my radish and had enough moisture early on for them to germinate. With my clay, even though we are in a minor drought, (couple inches low), my clay will retain enough moisture to keep them going. A little rain certainly won't hurt but mine are doing well.
Thanks,
Jack