Learn Russian: В августе тоже лето.

Because we are talking about a specific time using the word в (in). This triggers the Prepositional case. Since the month август is a masculine noun ending in a consonant, we add -е to the end.

Where is the verb "is" in this sentence?

In Russian, the present tense of the verb "to be" (am, is, are) is almost always skipped. The sentence literally translates to "In August too summer."

Why doesn't the sentence use a word for "it"?

English uses a placeholder subject like "it" to talk about seasons, weather, or time (like "it is summer"). Russian doesn't do this. You just state the season directly, which is why it is simply лето.

Is the placement of тоже important here?

Russian word order is flexible, but words like тоже (too/also) usually go right before the word they are emphasizing. Here it emphasizes that it is still summer, so it goes right before лето.