I drove from Oklahoma City to Monterey in 2014. I-40 just stops at Barstow. That is not a city worth spending any time in, and not what most people think of when the envision a trip to California. You get to go through other horrid places like Boron, CA.
Other beautiful parts of California like this.
Then to Monterey and Highway 1 which are the other end of the scale and just stunningly beautiful.
You did not say what part of Texas you are leaving from. Unless it is Amarillo, you likely will be on a more southern route. The one nice thing about I-40 is it goes to Flagstaff. That is a neat town up in the mountains and nice and cool.
Needles. Ca was at 118 degrees on my trip home. I hope your AC is in great shape. I have the Griffith's 4 condenser system and it is great, but 118 made it struggle to keep me cool. I never got hot, and when I got to Arizona and it had cooled down 15 degrees to just 103 the AC was doing great.
Enjoy the trip. If your car is in good shape it will do that little trip with no problems.