"Ich nehme an, es regnet."

Translation: I suppose it is raining.

[Coleo20]

"I take it, it's raining" should be accepted. It's not meant to be literal, but it does work in English, and if the German and English have a nearly direct equivalent, that should work. Unfortunately, "Assume" didn't readily spring to mind at the time. Another one should be "I gather it's raining"

[daschaich]

"I take it it's raining" was accepted for me.

While it's also acceptable to stick in a superfluous "that" as djusen suggests, this is not necessary.

[djusen]

What you have is ungrammatical. "I take it that it's raining" is accepted

[nltnjnns]

My answer of "I suppose it's raining" should be accepted.

[Knig97873]

I presume it is raining is not accepted?!

[SirCol13]

Why is there a comma in German?

[rynsmi]

From what I understand, commas are used to separate clauses in German. Here, the two clauses are "I suppose" and "it is raining."

Sometimes a conjunction is present, and this is more obvious. For example, "Ich nehme an, DASS es regnet." -> "I suppose THAT it is raining." English doesn't require such comma usage. HTH.