Learn Russian: Температура постепенно повышается, и становится всё теплее. - The temperature is gradually rising, and it is getting warmer and warmer.

In English, we show a progressive increase by repeating the comparative word. In Russian, you don't repeat теплее. Instead, you place the particle всё before the comparative adjective or adverb. This всё + comparative structure is the standard way to express "more and more" or "increasingly".

Why is the verb повышается reflexive (ending in -ся)?

The non-reflexive verb повышать is transitive, meaning to raise something (like a business raising prices). Because the temperature is rising on its own, which is an intransitive action, you must add the reflexive -ся ending so it translates to "is rising" rather than "is raising".

Where is the word for "it" in "it is getting warmer" (становится всё теплее)?

Russian does not use a dummy subject like "it" for weather conditions or environmental states. The verb становится (is getting / is becoming) is used impersonally here. You simply pair the third-person singular verb with the comparative adverb теплее, and the subject is left completely blank.

Why are both повышается and становится in the imperfective aspect?

Both verbs describe an ongoing, gradual change rather than a completed event. The word постепенно (gradually) highlights this continuous process, which always requires the imperfective aspect.