All the books in The Secrets of the Immortal Nicholas Flamel series have appeared in late May in the United States. The Warlock will follow the same pattern. Delacourt Press will release the book on May 24th.
I have no confirmed release date for the UK and Ireland edition however. I believe it may be early July, but more details to follow.
The official fan forum always has the most up-to-date information (they often get it even before I do!), so do check there also. Flamel’s Secret and Flamel’s Immortal Portal also have the most up to date information on the various editions from around the world.