|As iron sharpens iron,
so one man sharpens another.
That is what the Bible teaches about spiritual things, but the same thing works with violin practice.
In times where there is no formal instruction, it is helpful to get together with some of your friends with whom you have violin lessons and play around. You don't need to play pieces that you are working on in your lessons, you just need to be in the presence of other violinists so that you can keep up your skills.
Not only is it an encouragement to be around other violinists, it also maintains the skills that you developed in listening to one another. When lessons start up again in the Fall, you will be just that much further ahead. Not so much rust to knock off before you can start making real progress again.
So this Summer, get together with some of your violin buddies and keep one another sharp!