If you are talking contiguous 48 states, probably some places in Maine are farther north. If you are talking about the whole country, Alaska has the farthest north cities. But, 60's is about all we have been able to manage here (Wasilla), too.
I should have qualified with the lower 48, yes. However, Seattle is the Northern most city in the lower 48. Maine extends further North, but no cities there. Of course it all depends on how you define city. Portland is the only thing that resembles in a city in Maine in my book, and it’s South of Seattle.
Btw, with highs in the 60’s where does that put you on average for your area? It’s been so bad here, that it made the news that AC companies are flooded with calls because people think their AC’s aren’t working because it’s 80+ in the house, when they’re actually working fine. The reported temps have been in the low 100’s, but that’s at a weather station 40 feet in the air in the middle of field or airport. It’s easily been hitting 115 in the asphalt islands, so 80 degrees inside means that AC is kicking ass and bringing the temp down a whopping 35 degrees.