Thick black smoke billowed into the sky, making day seem more like night.

Add Yahoo as a preferred source to see more of our stories on Google. Iran says it launched its "most intense and heaviest operation" of the war as Israel pounds Tehran and Iran-backed Hezbollah in Beirut. Why did Trump attack Iran? Is the U.S. at war now?

Thick, toxic smoke and black, acid rain have blanketed Iran’s capital, Tehran, this week, after missiles damaged oil depots and refineries. Researchers warn that it probably contains chemicals that are harmful to people and the environment. What is black rain, how does it form and how long will it take to disperse?

Switzerland is temporarily closing its ‌embassy in Tehran due to the war in the Middle ​East and increasing security ​risks, the foreign office said ⁠on Wednesday.

A poster of Ayatollah Mojtaba Khamenei, the successor to his late father Ayatollah Ali Khamenei as supreme leader is placed on an anti-riot police car as policemen stand on top of the car, during a rally to support him in Tehran, Iran, Monday, March 9, 2026. (AP Photo/Vahid Salemi)

This network of tankers continues to move large quantities of sanctioned Iranian crude across global waters, ensuring a steady revenue stream for Tehran despite international sanctions.

The skies of Iran turned orange as Iranians experienced some of the heaviest bombardment since the war began. It comes after President Trump warned Iran would be hit “hard” and Iran’s president rejected Trump’s demand for the regime’s unconditional surrender.

Though some Iranians mourned the death of their supreme leader, others rejoiced. Their celebrations were furtive and short-lived to avoid riot police or other authorities.

The low-grade oil has been used to fuel power plants amid Iran’s international isolation. Tanks of mazut may now be burning near the city.