The longest full solar eclipse in the last 2,000 years will occur on Wednesday, July 22. And it may be rained out in China.

Cities that had been widely regarded as the best places to watch the eclipse, including Shanghai, Nanjing, Hefei, Wuhan, and Hangzhou, will probably experience rainfall or overcast weather when it happens, according to predictions from China’s National Meteorological Center.

The full eclipse will still plunge the cities into six minutes of complete darkness, as the moon comes directly between the Earth and Sun, briefly putting most of central China in its shadow. The rest of the country will see a partial eclipse.

“Generally speaking, total solar eclipse is once in 300 years at the same place and it usually lasts only about three minutes,” said Zhao Guang, deputy head of the National Astronomical Observatory.

Local governments have been asked to make appropriate arrangements at places where observes will gather to watch the eclipse, and to guarantee smooth and safe public transportation before and after the event. The central government has also urged relevant departments in the eclipse regions to be prepared for any disruptions or disorder that might occur.