Multitude of factors. Inception of Niña/E-Hem LF forcing in tandem with descending +QBO, -PMM/+AAM (which modulates ITCZ/HC width), and +DMI/+IOD tendency which will focus convection towards the IO side of the IPWP heading into the heart of summer.
Everything is set up the worst way possible. A miracle is always possible, but those are few and far between these days.
June might have a few cool shots left in the tank (eastern US first half of month then western US second half) but that’ll likely be the exception rather than the rule IMO.