Why Does the Sky Look Green Before a Tornado?

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iStock

A common bit of folklore from tornado-prone parts of the U.S. says that when the skies start taking on an emerald hue, it's time to run inside. But why do tornadoes tend to spawn green skies in the first place? As SciShow's Michael Aranda explains, the answer has to do with the way water droplets reflect the colors of the light spectrum.

During the day, the sky is usually blue because the shorter, bluer end of the light spectrum bounces off air molecules better than than redder, longer-wavelength light. Conditions change during the sunset (and sunrise), when sunlight has to travel through more air, and when storms are forming, which means there are more water droplets around.

Tornadoes forming later in the day, around sunset, do a great job of reflecting the green part of the light spectrum that's usually hidden in a sunset because of the water droplets in the clouds, which bounce green light into our eyes. But that doesn't necessarily mean a twister is coming—it could just mean a lot of rain is in the forecast. Either way, heading inside is probably a good idea.

For the full details on how water and light conspire to turn the sky green before a storm, check out the SciShow video below.

A Pile of Manure and a Heat Wave Combined to Cause Spain’s Worst Wildfire in 20 Years

Lumppini, iStock/Getty Images Plus
Lumppini, iStock/Getty Images Plus
A pile of manure in Spain ignited on June 27, sparking a wildfire that has torn through more than 10,000 acres of forest and other Catalonian landscapes, CNN reports. The manure combusted in part because of a scorching heat wave that has swept across Europe this week; temperatures in the affected region hit 104°F, and Germany, Poland, and the Czech Republic all reached record-breaking June temps. Catalan regional interior minister Miquel Buch reported that authorities believe the manure was improperly stored on a chicken farm in the village of La Torre de l’Espanyol, where it was exposed to the worst of the heat, according to NBC News. The wildfire—Spain’s most devastating in 20 years—is affecting the region just west of Tarragona, a port city that is best known for its Roman ruins, which is situated along the Balearic Sea about 60 miles southwest of Barcelona. [[{"fid":"315211","view_mode":"width-constrained-728","fields":{"format":"width-constrained-728","field_file_image_title_text[und][0][value]":false,"field_file_image_alt_text[und][0][value]":"Map of Catalonia, Spain","field_image_subhead[und][0][value]":"","field_image_subhead[und][0][format]":"unfiltered","field_caption[und][0][value]":"","field_caption[und][0][format]":"unfiltered","field_credits[und][0][value]":"PeterHermesFurian%2C%20iStock%2FGetty%20Images%20Plus","field_credits[und][0][format]":"unfiltered"},"type":"media","field_deltas":{"1":{"format":"width-constrained-728","field_file_image_title_text[und][0][value]":false,"field_file_image_alt_text[und][0][value]":"Map of Catalonia, Spain","field_image_subhead[und][0][value]":"","field_image_subhead[und][0][format]":"unfiltered","field_caption[und][0][value]":"","field_caption[und][0][format]":"unfiltered","field_credits[und][0][value]":"PeterHermesFurian%2C%20iStock%2FGetty%20Images%20Plus","field_credits[und][0][format]":"unfiltered"}},"link_text":false,"attributes":{"alt":"Map of Catalonia, Spain","height":728,"width":728,"class":"media-element file-width-constrained-728","data-delta":"1"}}]] The firefighting force includes about 350 firefighters, 12 fire engines, seven aircraft, two hydroplanes, and additional vehicles equipped with water tanks—all of which are techniques regularly used to fight massive blazes. Though high temperatures are expected to continue and the rough terrain itself is also a contributing factor in the rapid spread of the fire, the strong winds should soon abate; authorities have warned people to stay inside. Though more than 50 people have been evacuated from the area, no deaths have been reported thus far. While the spontaneous combustion of flammable materials like manure, hay, or compost is definitely possible, as evidenced by this situation, it’s not the most common way for wildfires to start. More common causes include lit cigarettes, unattended campfires, burning debris, and engine sparks. [h/t CNN]

Colorado Welcomed Summer With 2 Feet of Snow

Emmanuel Dunand/AFP/Getty Images
Emmanuel Dunand/AFP/Getty Images

While people in some parts of the country celebrated the first day of summer with barbecues and trips to the beach, residents of north and north-central Colorado had a snow day. Areas west of Denver—including Grand Lake, Aspen, and Steamboat Springs—experienced snow storms on summer solstice, with snowfall totaling nearly 2 feet at the highest elevations, CBS Denver reports.

Snow started falling in the Rocky Mountains the morning of Friday, June 21 and continued Sunday. Areas at ground level weren't cold enough to experience the unusual weather, but at elevations of 7000 feet and above, it looked like a winter wonderland. Steamboat Springs, a ski resort town in Colorado’s Yampa Valley, accumulated 20 inches of snow on the longest day of the year.

While Colorado mountain towns are used to seeing snow at odd times of year, the weekend's weather was still out of the ordinary. The average snowfall for Steamboat Springs in June is 0.1 inches. Prior to last Friday, it had been 91 years since a snowstorm hit the city in late June.

Snow has fallen in the Rockies later than average in six out of the past seven years. Though it feels like an extension of winter, the trend may actually be a product of the warming atmosphere. A warmer climate affects the jet stream, potentially pushing its course further south and leading to unusual weather patterns, such as unseasonable snowstorms in Colorado.

That means residents of some parts of the state will have to wait to have their summer hikes and picnics. The weather was serious enough to shut down one road in Rocky Mountain National Park.

[h/t CBS Denver]

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