My daughter is very similar. We believe she is on the autistic spectrum, however, it's tough to even get a referral where I live, so we have no diagnosis. There's no harm in trying a few strategies for autism though - since we have accepted that her needs align with those on the autistic spectrum, she has been much more relaxed (notice that I said 'much more', rather than 'very; - she is still a little stress head!). Am absolutely not saying that I think your daughter has autism - just that children have different needs, and sometimes this requires different parenting strategies.
Holidays are difficult - my daughter is explosive towards the end of term, over the holidays, and then at the beginning of term. Any transitions are tough. That goes for little transitions too - like from watching TV, to not watching TV. I give countdowns for everything, and often use a timer. This gives her time to process the upcoming change. I also avoid directions - my daughter is demand avoidant - not to the extreme of PDA, but she definitely struggles with them. So, instead of saying "Please go and get dressed", I will say "When you are dressed, then we can have breakfast." Makes a big difference. And I let the timer be the dictator "When the timer goes off, then you need to get into the bath." I'm not really the one giving the order then. It works well.
I noticed that you also mentioned that you have trips planned - if I have that with my daughter, I need to talk through each step of the plan, so that she knows what to expect. Anything unknown will make her particularly anxious.
Finally, it's also worth keeping an eye out for any triggers. I have had extreme episodes with my daughter before, which, on questioning, have resolved to "You said that this was going to happen, and then it didn't." An episode of behaviour can usually be traced back to a single cause - with her, anyway. Often sensory issues - particularly sound - can be the cause.
As PPs have said, I found "The Explosive Child" helpful. One thing I liked about it, is that it ignores diagnoses, and just focuses on managing behaviour. I've noticed on here that there seems to be a bit of attitude that if behaviour isn't down to some kind of SEN, then it is just bad behaviour, and requires firm discipline. I think that's a little simplistic - many kids have needs that are on the extreme ends of normal. Sorry for the essay - this all may be completely irrelevant, and it could be an early hormonal thing, getting annoyed at the heat, or something that upset her at school! Hope things improve for you all though - I know how tough it can be.