Now, its skies are mostly blue — a sign the Chinese capital is entering a new era of clean air, the country's Minister of Ecology and Environment claimed last Wednesday.

"The 'Beijing blue' has gradually become our new normal," said Huang Runqiu, the minister, according to state-run tabloid Global Times, as the city recorded its best monthly air quality since records began in 2013.

Though Chinese cities have long topped global rankings of the world's worst air quality, they have shown steady improvement over the years. Beijing only recorded 10 days of heavy air pollution last year, Huang said — a drop of nearly 80% since 2015. Recent photos from Beijing show clear blue skies and summer sun, once a rarity in the city of approximately 21 million.