It is recommended to take down hummingbird feeders during the fall season when the birds start migrating to warmer regions. This is because leaving the feeders up during the winter season may attract hummingbirds to stay in an area that is not suitable for their survival.

Additionally, if the nectar in the feeder freezes, it can become a hazard for the hummingbirds. Therefore, it is best to take down the feeders in the fall and put them back up in the spring when the birds return.

Maybe one day I won’t live in a dark, concrete box surrounded by concrete and non-native plants and this will actually apply to me.

https://learnbirdwatching.com/when-should-you-take-down-hummingbird-feeders/

What are we supposed to do in warm/temperate climates, like Southern CA?

I read late October

If you live in the deep south you may or may not have to take yours down. Some hummingbirds stay in the southern states over winter and will want to be fed. Check online for your state 👍