intake temp range

What is an acceptable intake temp range for long term running? I found the intake gauge on my CAT ID and was just wondering what ranges is safe for the engine since I can't seem to find any answers anywhere. Engine is a modified C15 Acert.

I was keeping track today and with temps in the lower 80's, driving 65 and bucking a strong crosswind the temps were staying in the 115*-125* range. They were running right around 100* before it got warm and slowly started to rise as the outside temp and wind went up. On a long hard pull I had the temp spike at 150* but drop back down once I leveled off at my desired speed. This morning when driving empty in 50* temps the intake never got above 90*.

 

Thanks guys. I've asked a few mechanics and looked on the web and couldn't get any numbers to go by. It seemed like nobody really gave intake temps much of a thought.