Can I apply a Kalman filter to DHT11 data?
Learn about the kalman filter and what it does. It requires a certain understanding of what it is, what it is good for and why you would eventually use it. It seems to me, that at the moment this isn't your strongest topic.

Thereafter, figure out which !multiple! sensor values you have, since only with a "model" and an "observation" a filter of this kind makes sense in the first place.

To specifically adress your question: you can apply any filter to any data. The hidden question, if it makes sense in this case is not trivial to answer, since you didn't exactly provide the vast information. My guess is, you only have this one sensor, and it would be (at this state of knowledge) a reasonable idea to use a bandpass filter of sorts instead.