I would echo what ragdoll and bubbleblower have said.
There are some who have been able to phase off and then get back to P1 after a little while without issue. But many more have come back and found that it's harder to stick to P1 after being off it for a while, plus more than a few have reported that the weight loss was slower. Maybe you'll be a lucky one who can just jump back in with no issues...but do you really want to take that chance?
I started P1 in July last year. Made it through BBQs, holidays, big family and social functions, my high school reunion and my birthday, all while on P1. If I had decided to phase off for any of those things, I would not be in maintenance now! I also would not have learned many of the valuable lessons (in how to handle food AND how strong I could be in tough situations) that staying on P1 through those things taught me.
You ultimately have to do whatever it is you feel is right, but just know that it is TOTALLY doable to stick to P1 through whatever the summer might have to offer....and you will be all the stronger for it