The windshields aren't coated to block UV. Wear UV-block glasses, use the sunshades to prevent squinting and drink plenty of water. If you aren't peeing at least every three hours, you're dehydrated.
I also wore a long-sleeve, cruise shirt to keep the damaging UV off my arms. When I retired, the left sleeve was noticeably more faded that the right sleeve (NOPAC flying westbound during the day). At the very least wear UV blocking sunscreen if you're going to do it for decades.
Ex-long haul guy.