Can the aurora be seen only on clear days?

No. Aurora observation has a lot to do with weather conditions. On a clear day, the clouds are relatively thin and will not block the aurora, so the probability of seeing the aurora is much higher than on a cloudy day. Most aurora appear between 90 and 130 meters above the earth. Kilometers, and the clouds are below 10 kilometers, so as long as there are clouds, it will affect the viewing of the aurora; but even on a sunny day, it is not necessarily possible to observe the aurora; in addition, the darker the surrounding environment, the more conducive to the observation of the aurora, so A location away from the city lights is even more ideal.