oh, to have 78degree days in February! (I'll pass on the 118F summer temps though
)
no, the line you need to feel is about 3/4 inch in diameter and it will be coming from the compressor, not the receiver. I think it usually goes across the front of the valve cover, but it may not on your car. if the line leaving the receiver is cold, you have a plugged line, and probably an overcharged system to compensate.
at 70F ambient, the low pressure would be around 22psi... and you might even get some frost on the large line...