Authorities in Iran have sprayed clouds with chemicals to induce rain, in an attempt to combat the country's worst drought in decades.

Known as cloud-seeding, the process was conducted over the Urmia lake basin on Saturday, Iran's official news agency Irna reported.

Urmia is Iran's largest lake, but has largely dried out leaving a vast salt bed. Further operations will be carried out in east and west Azerbaijan, the agency said.

Rainfall is at record lows and reservoirs are nearly empty. Last week President Masoud Pezeshkian warned that if there is not enough rainfall soon, Tehran's water supply could be rationed and people may be evacuated from the capital.

Cloud seeding involves injecting chemical salts including silver or potassium iodide into clouds via aircraft or through generators on the ground. Water vapour can then condense more easily and turn into rain.

The technique has been around for decades, and the UAE has used it in recent years to help address water shortages.

Iran's meteorological organisation said rainfall had decreased by about 89% this year compared with the long-term average, Irna reported.

"We are currently experiencing the driest autumn the country has experienced in 50 years," it added.

Officials have also announced plans to penalise households and businesses that consume excessive amounts of water.

The head of Iran's National Centre for Climate and Drought Crisis Management, Ahmad Vazifeh said dams in Tehran, West Azerbaijan, East Azerbaijan and Markazi are in a "worrying state", with water levels in the single-digit percentages.

On Friday, hundreds gathered at a mosque in Tehran to pray for rainfall.

Iranian meteorologists reported there was some rainfall in the west and northwest of the country on Saturday - with video showing snowfall on a ski resort north of Tehran for the first time this year. (BBC)

• PHOTO: Women, wearing hijabs, with their backs to the camera are praying for rain in northern Tehran. Image source: EPA/Shutterstock