Since the beginning of mankind, humans have relied on weatherlore to predict outdoor conditions.
One popular theory—if there is a halo around the sun or moon, rain or snow is coming soon—is proven to be more factual than others, including the popular wooly bear caterpillar predicting winter.
Frank H. Forrester, author of “1,001 Questions Answered about the Weather,” wrote that the presence of lunar or solar halos is evidence of a layer of cirriform clouds. Cirriform clouds, he wrote, are high ice crystal clouds that may be 30,000 feet above the Earth’s surface.
Forrester wrote that this type of cloud is often indicative of a warm front associated with a low-pressure area.
“Rain or snow will not always follow the appearance of a ring around the sun or the moon, but there is a higher probability of precipitation after a halo is seen and the probability is greater if the circle is brighter,” Forrester wrote.
When asked if this theory was true, My Valley Weather Meteorologist Don Guthrie said yes. He said that high, thin clouds, also known as cirrus clouds, precede an area of low pressure and precipitation.
“The high, thin clouds have ice crystals on them and it’s the moonlight that reflects off the ice crystals, causing the ring around the moon,” Guthrie said.
One rule of thumb is that rain or snow will come within 12 to 18 hours after seeing a halo on two out of three occasions.
