Learn Hardcore Russian: В жару я читаю книгу в тени.

In Russian, when you express “during” a certain time or weather condition, you often use the pattern в + accusative. So в жару literally means “in hot weather,” and here жару is the accusative form of жара. It’s an idiomatic, fixed way to say “when it’s hot.”

Could we also say на жаре instead of в жару? If so, what’s the difference?

Yes, both в жару and на жаре are heard.

в жару emphasizes the time period “during hot weather.”
на жаре can feel more like “out in the heat” or “under the hot sun.”
In many contexts they’re interchangeable, but в жару is slightly more abstract/time-focused, while на жаре often has a physical/emphasis-on-location nuance.

Why is в тени in the prepositional case (тени) instead of the accusative like in в жару?

Here в expresses a static location (“in the shade”), so it takes the prepositional case: в + prepositional = location. That’s why тень → тени. In contrast, в + accusative is used for movement or, as above, idiomatic time expressions.

Could we change the word order? For example, “Я читаю книгу в тени в жару.” Is that acceptable?

Absolutely. Russian has a flexible word order. You could say:
• Я читаю книгу в тени в жару.
• В тени я читаю книгу в жару.
• В жару я читаю книгу в тени.
Moving the adverbial phrases shifts the emphasis (time vs. place), but the basic meaning stays the same.

Why is the pronoun я included? Can it be omitted?

Russian verb endings already show the subject. Читаю means “I read/am reading.” You can drop я and just say В жару читаю книгу в тени for a more colloquial feel. Including я adds clarity or emphasis on the fact that I do this.

Does я читаю книгу imply I’m reading right now or that I do this habitually?

The imperfective present tense (читаю) covers both ongoing and habitual actions. Context tells you which: here, with в жару (“when it’s hot”), it usually means habitually—“Whenever it’s hot, I read a book in the shade.”

Why are there no articles before книга or жара?

Russian doesn’t have articles (no equivalent of “a,” “an,” or “the”). Definiteness or indefiniteness is understood from context or word order, without extra words.

What’s the difference between the noun жара and the adverb жарко?

• жара is a noun meaning “heat” (the condition).
• жарко is an adverb meaning “it’s hot.”
You could say В жару мне жарко (“It’s hot to me in the heat”), but to focus on your action you use в жару as the time-phrase and leave жарко out.