When to buy maternity clothes??

First time mom here and this may be a really dumb question but I’m going to be pregnant through this summer and I know I will want to die if I don’t have shorts I can wear. Will I be able to find things like maternity shorts and tanks later in the summer when I actually need them Or should I buy now and hope they fit? I know when I’ve waited to buy normal shorts I end up not being able to find any in my size - is that a problem in the maternity world too or am I overthinking this?