Many throughout the Monadnock Region were in awe Tuesday evening after a vivid double rainbow stretched across the sky.
In Peterborough, the double rainbow emerged after a period of thunder, hail, and rain – weather that set the stage for the two colorful arcs to emerge.
“The conditions were great for seeing the double rainbow phenomenon,” National Weather Service Meteorologist William Watson said Monday morning. “With a rainbow, you need water droplets and sunlight behind you to shine towards the water droplets.”
Rainbows are an optical phenomenon formed by the reflection, refraction, and dispersion of light in water droplets, according to the National Oceanic and Atmospheric Administration. Technically a circle, rainbows are most commonly seen as an arc from the ground level.
The colors of the rainbow are seen because the individual wavelength of sunlight are separated within the droplets of water.
Believe it or not, every rainbow is a double rainbow, Watson said. How vivid or noticeable the second rainbow is – which will always be inverted – depends on how much water and sunlight are introduced.
“It’s a double reflection of the sunlight,” Watson said. “It takes the right amount of water and sunlight to see the second rainbow.”
While more common in the summer, Watson said a thunderstorm with hail in the fall is not impossible.
Watson said Tuesday’s conditions were perfect for the storm – hail is caused when an upward current of air in a thunderstorm carries raindrops upward. The raindrops are brought to an extremely cold part of the atmosphere, where the rain freezes to ice.
And for those Boston Red Sox fans who saw a double rainbow over Fenway Park last night – the double rainbow seen in Boston was likely a different double rainbow.
Watson said it highly unlikely that a double rainbow could be seen in two locations so far apart. Instead, Watson said it was likely that weather conditions were perfect in two different geographical areas in New England.
Nicholas Handy can be reached at 924-7172 ext. 235 or nhandy@ledgertranscript.com. He is also on Twitter @nhandyMLT.