The normal range for oil pressure on a Twin Cam is 30-38 psi @ 2000 rpm and 230°F oil temp. With air temps in the 105°F range, I'd be willing to bet your oil temps were well above normal, and the viscosity of the oil decreases of course as the temperature increases. If your bike is like most, it probably averages around 32 psi @ 2000 rpm and normal oil temps. Add another 30-40°F to the temps, and a drop to 28-30 psi @ 2000 rpm wouldn't surprise me at all. What was the pressure at idle under those same conditions?
I personally don't ride anymore when the temperatures get above the lower 90's, so I can't offer any first hand numbers from experience that would match your 105°F situation. I can tell you that while my bike consistently runs 32-33 psi @ 2000 rpm most of the time, I do notice it tends to slip back towards 30 psi when I ride in 90°F weather for an extended time, and idle pressure drops a pound or two as well. It's nothing to be concerned about.
Jerry