How long can the outside temperature be constant?

Where on Earth is the most constant outside temperature? And what would be the longest time of the same outside temperature on the Fahrenheit scale? (Or, if the answer is significantly different, answer for the Celsius / Kelvin scale too)

to clarify, “same” means the temperature does not vary by more than 1 degree.

Does your definition of ‘outside’ extend below the surface of the ocean? I’m guessing not.

Oooh, interesting point. I guess I should have specified surface air temperature. (otherwise, I suppose the water temperature of a pond would be pretty constant)

Yes. And the deeper you go, the more stable is the temperature, typically. Somewhere as deep as the Mariana Trench probably remains at a very stable temperature for much longer than twenty minutes.

My WAG regarding most stable air temperature is that it’s going to be near one of the poles - where day and night work differently.

Is the air temperature at super-high altitudes or even the edge of space very constant?

Are you going to exclude caves also? I suppose that patently violates “outside”, but it’s not a man-made “inside”. Anyway, many cave systems exhibit a sort of “thermal flywheel” effect where the temperature of passages distant from the entrance varies little and is a good approximation of the mean temperature of the area.

Although we’d never know, because we’ve never been there for longer than that. Just once. …What year was it, I wonder?