Is it the anniversary of the MOUNTSTHELENS (39A: It left parts of itself in 11 states in 1980) eruption? No, that was on May 18th. So it's just a random reference. Fine. It's a good enough reason for covering the puzzle with [ASH].
The rebus came to me very early today, right when I hit 8D: Not go together at all (CL[ASH]). And then that quickly gave ON[ASH]ORTLE[ASH]), and I was off to the races. The top and bottom were done in short order, but I didn't have much at all in the middle. I started at it for a while, then fell asleep. This morning, Frannie took up the fight, and handed the iPad back to me with the "Well Done" message in just a few minutes.
Eleven rebus squares seems like a lot, and I liked that you had no idea where they would pop up. (Sometimes they've been symmetrical, which seems to defeat the purpose.)
I enjoyed REPTILE (27D: Cold-blooded sort), PAR (36A: It's not unusual), LOO (42D: Throne room at Buckingham Palace) (LOL), NOOSES (51D: Deadly constrictors), and THR[ASH]ES (52A: Licks) (even though it's oh-so-close to TR[ASH]ES (66A: Bad-mouths)).
Didn't like OWE (35A: Must give) or WEPT (43A: Had pity (for)) - both seem slightly inaccurate. And I can never remember any of those damn 61A: Brit. military decorations (DSO).
I don't have much more to say. I liked it fine. Not my favorite ever, but a fine Thursday.