Let's say today is September the first, 2020 and I want say that I did something in the summer of 2019. I cannot say I went on vacation last summer because even though the summer of 2020 has just ended, it would still reffered to the summer of 2020,right? What would be the most natural way to refer to the summer of 2019, when I am in September the first 2020? Do the following sound natural?
I went on vacation in the summer before last.
I went on vacation in the summer last year.