When the outside temperture is 100+ degrees, we know it is past time to turn on the A/C. To be truthful, it does not have to be that hot outside, depending on the part of the country we might be in (how humid it is). When it gets up to 90 degrees or so, we use the A/C if possible. However, the fantastic fan is really a help when it is getting warm inside and for some reason we can not use the A/C. We used it a lot this summer when we spend a month in the Scamp
in North Dakota. It would keep it cool inside just using the fan. But on some days, we had to use the A/C when it was getting into the upper 80s. Being from New Mexico, we knew we wanted A/C when we order the trailer. We have gottten by on mildly hot nights with just the fan at Devil's Tower, WY (100 degrees in the day time at the time, we cooled the trailer down before generators had to be stopped), in the Phoenix area and in Pueblo, CO (100 degree weather that day as well). With that said, if you are only camping in the Pacific Northwest, I am not sure if you would need A/C or not. We have not been up in that area enough to give a quilified answer. We did not use A/C on our first trip through for sure....no way to power it even if we needed it (but did not). I can not remember using it on the second trip when we did have power to do so if we needed it (no need for it). We traveled and camped many years without A/C all over the west and southwest and without a vent fan as well. The only time we needed and wished for power to get our A/C going was by Lake Powell near Page, AZ where it did not cool off at night. 100 degrees at 11 PM. We headed to higher ground the next morning.....north side of Grand Canyon. In most places of the southwest and in the west, it cools down at night. Phoenix and Las Vegas, NV would be exceptions. We were glad for A/C in Salt Lake as well.
Edit add: I see your Location: Pacific S W....would that be inland of the Northwest? I have not been camping in that area to know. If it is along the California Coast or Organ Coast, I wouldn't think an A/C would be needed at night, nor in the day normally. Away from the Coast, I would say
for the A/C just in case. I do like to be cool when it is hot out. In most of Texas and Back East, A/C for sure!