The sky in this eastern Chinese city was transformed into a hellish backdrop on May 7.

Locals in Zhoushan, Zhejiang Province, were seen staring up at the blood-coloured sky in amazement.

An expert from the space physics research team at the China University of Geosciences said: “The geomagnetic activity was generally calm and there was no significant anomaly in solar activity on May 7.

“The weather in Zhoushan on that day was cloudy to rain with fog and a yellow warning signal (the second strongest level) was issued for the heavy fog.

“Since the lights on fishing boats were red and the red light has a long wavelength and strong penetration, the liquid droplets in the atmosphere scattered the red light over a wide range causing the abnormal colour in the sky.”

The video was provided by local media with permission.

5月7日晚8时许，浙江舟山普陀出现罕见红色天空，引发当地居民围观，有目击者称，活了几十年了，第一次看到这种天象。
记者经过逐一调查，证实出现红光的位置，位于普陀平阳浦方向。根据红光的地点进行定位分析，发现该位置正好位于舟渔公司码头。舟渔公司相关负责人表示，当时码头正停着一艘捕捞北太秋刀鱼的远洋渔船。船上安装了用来照明的红色灯光，以方便捕捞秋刀鱼。而红色的光波长是可见光中最长的，具有很强的穿透力，于是就出现了这种红光满天的现象。
中国地质大学空间物理研究团队一位专家介绍，根据太阳和地磁活动观测记录显示，5月7日地磁活动整体平静，太阳活动也无显著异常情况发生，可以基本排除因地磁和太阳活动导致天空红色的可能。他说：“当日舟山的气象条件为阴转雨，有雾，低层大气湿度大，有大雾黄色预警。因为远洋渔船灯光为红色，红光波长较长穿透力强，同时在大气中液体微滴的散射作用下，会将红光散射到较远范围，于是呈现出一片天区的异常红光现象。”
舟山气象局工作人员表示，天空呈现红色是属于光的折射和散射现象，当天气条件较好时，大气中水分较多形成气溶胶，光源或为港口的船舶灯光。（视频由浙江台提供）