Also, anyone traveling on a train or motor vehicle will just sometimes have worse reception, particularly with anything like a tunnel.

Crazy hills will do wireless in anywhere. In a rural area I am maybe a mile from the tower as the neutrino flies but a photon can’t make it. I have a bar of 5G in the pasture in front of the house but in the house it promises a bar of LTE but whether I can get out a text (w/o WiFi) depends on atmospheric conditions.

Out in Cali they have ring of fire conditions.

Too much crowding can do it too. A decade ago I was going to Cali a lot and thought it was funny to see so many ads for geospatial apps on TV that always showed a map of San Francisco when for me SF was where GIS went to die. Taking my Garmin handheld to the roof of the Moscone center because it was the only place it could get a clear view of the sky to sync up with GPS, so many twisty little streets that routing algorithms would struggle…. Being guided around to closed restaurant after closed restaurant and walking past 10+ open ones because a co-worker was using Yelp, etc.

Back around 2001 I visited South Carolina, and it was like being transported to the future of mobile internet. They had some kind of high-bandwidth cellular setup in the area that was far ahead of the rest of the country at the time, I think I recall it being around 20Mbit wireless. I was told the area was a testing ground for new tech. I was kind of shocked that somewhere that seemed so stuck in the past had such cutting edge tech deployed. I thought why is this not in SF??