If you are worried about extreme temperature fluctuations you can employ a heater or cooler, as well, but I advise you to worry about humidity above all else
I have been collecting comics since I was a teenager. I have been reading them since I could read, but I didn’t have the foresight to collect them until I was a little older. For the last twelve years I have been moving this comic book collection around with me. The funny thing is that I don’t even buy comics anymore, I just can’t bear to part with the few thousand of them that I already own. They are bagged and boarded and kept in secure boxes, except for the handful I have out on display. To maintain a vintage collection requires superior indoor air quality, which is why I invested in some extra HVAC equipment just for the care of my comics. The biggest threat to the long term safety of your comics is moisture, so my first purchase was a dehumidifier. I didn’t go the cheap route, either, I bought a high end dehumidifier and air purifier, and it was worth every penny. Two years later I bought a second dehumidifier, to use in addition to the first one, because the local humidity levels were higher than usual. It is better to be safe than sorry, so when the air quality outdoors deteriorates, expect similar results for your indoor air quality. If you are worried about extreme temperature fluctuations you can employ a heater or cooler, as well, but I advise you to worry about humidity above all else. Comics aren’t as damaged by heat and cold as much as moisture, so spend all the money you can on a top-end dehumidifier.