BEIJING — There are many things that the Chinese Communist Party can control as it gears up to celebrate the 70th anniversary of the People’s Republic on Tuesday. It can dictate what people read and say on the Internet. It can say where people sleep and eat and drink. It decides whether they fly kites or sing karaoke.

But not even the Chinese Communist Party can control the weather — although it is trying.

In the weeks leading up to Tuesday’s anniversary events, authorities have turned to their usual playbook to make sure the capital’s often-smoggy skies are blue for the huge military parade through Tiananmen Square, complete with fighter jets streaking multicolored smoke trails.

Trucks have been banned from Beijing since Aug. 20, and all construction in the city center was forced to halt before Sept. 1. Industrial companies within 300 miles of Beijing were asked to “voluntarily” control emissions or stop production. Mining activities, especially drilling and blasting, have been suspended until Oct. 7, and no one in Beijing is allowed to set off fireworks.

Vice Premier Hu Chunhua even visited the China Meteorological Administration and called for “meteorological support to ensure the success of the activities” around the anniversary.

The meteorologists should provide “targeted services” for the celebrations and have “response plans” to deal with adverse weather, Hu said.

It has worked in the past.

Even as Beijing’s air quality deteriorated rapidly in recent decades, the party has tried to eliminate pollution before big events and create the semblance of clean air, ordering the factories around Beijing to grind to a halt and heavy trucks to get off the road.

The ability to clear the skies on an order has given rise to the term “APEC blue” to describe a particularly bright day. It is a reference to the Asia-Pacific Economic Cooperation meeting that Beijing hosted in 2014, creating blue skies for the event after months of heavy pollution that often sent the Air Quality Index off the charts.

During a China-Africa forum last year, some Beijingers started joking that it had cost them $60 billion to enjoy blue skies. That was how much China pledged in aid to African nations.

But it turns out the party can do only so much. 

A low-pressure front is pushing industrial and vehicle emissions from surrounding provinces into the capital, and the humidity in Beijing is converting it into ­moderate-to-severe pollution. As a result, heavy smog is forecast for Beijing over the coming week.

Beijing has issued its first “orange” alert of the fall for heavy air pollution, causing schools in the capital to cancel outside activities and keep children indoors Thursday.

Eleven expressways in or around Beijing were completely or partially closed because of low visibility Friday, and many flights from Beijing Capital International Airport were canceled or delayed.

The city’s Environmental Protection Monitoring Center on Friday forecast that air quality in central Beijing will be at “unhealthy” levels above 150 on the Air Quality Index for the next week — levels that are often associated with soupy skies.

This is particularly stinging given that recent efforts to curb air pollution are paying off. The Swiss firm IQAir AirVisual said this month that the Chinese capital could drop out of the list of the world’s 200 most polluted cities, with concentrations of small particulates falling to their lowest level since record-keeping began in 2008.

Beijing’s mayor, Chen Jining, said this month that the density of PM2.5, the smallest and most dangerous particles in the air, had fallen by 43 percent since 2013. This is in large part due to a precipitous drop in coal consumption in Beijing, to about a fifth of its peak level.

“The air quality in Beijing has improved continuously,” Chen said. “It used to be the ‘APEC blue’ or ‘parade blue,’ but blue skies have now become normal this year.”

To try to make sure the skies are pristine Tuesday, the Environment Ministry has called on all municipalities to swing into emergency-response mode. The China Meteorological Administration entered “a special working state” on Thursday, continuing through to Wednesday, for nonstop monitoring of the parade weather. 

That may not be enough.

Some experts expect the authorities to start “cloud seeding” — spraying salt or chemicals into clouds, usually from aircraft, to encourage condensation and make it rain faster than it otherwise would.

“The most likely option for Beijing is to create rain through cloud seeding one or two days before the parade,” said Tian Pengfei, an atmospheric scientist at Lanzhou University in China’s sandstorm-prone northwest. “If done earlier than that, air pollutants may start to accumulate again and possibly lead to a new round of smog.”

Cloud seeding and other weather-modification measures have become relatively commonplace before big events in China.

Authorities spent $30 million shooting salt and minerals into the sky before the 2008 Beijing Olympics, and then spent more than $1.2 billion between 2012 and 2017 trying to clear the skies for important events like the Group of 20 summit in Hangzhou and a Belt and Road Forum in Beijing.

In 2015, China’s top economic agency announced a plan to build numerous weather-modification laboratories around Beijing. By 2020, it wanted “sophisticated weather-modification systems capable of increasing artificial rainfall and snowfall” and giving it more control over the weather. It has not given an update on its progress.

Other pollution-prone capitals such as Bangkok and Malaysia’s Kuala Lumpur also use cloud seeding to try to disperse hazardous particles, and drought-afflicted areas in countries including Australia and the United States also sometimes try to induce rain in this way.

But there may be yet another quandary facing Beijing. It might not have enough clouds in which to plant the rain seeds.

“The problem is that the autumn in Beijing is rather dry, and we might not have enough clouds to make it rain,” said Huang Binxiang, an air pollution researcher at China Agricultural University.

That would mean the meteorologists would need to try to imitate rain by spraying water from aircraft to try to wash the small particles out of the air.

“I have also heard some crazy proposals to use giant fans to blow away the smog,” Huang said. “I wouldn’t say it is impossible, but it has not worked so far as I know.”

Lyric Li and Liu Yang contributed to this report.