The third trimester is a typical time to shower. In general, from 6 to 8 months. The best time for my clients is late in the second trimester, between 6-7 months. A late shower will be more exhausting. The mom-to-be is always absolutely exhausted at the end of showers, and then she still has to haul everything home and unpack their car.
It's still a good idea to have a shower 2-3 months before your baby is due if you're expecting it through a non-traditional method, such as adoption or surrogacy. If there are any last-minute items on your registry, you have enough time to get them and set up your nursery.