![Snow accumulated on trees, Mount Rainier, Washington, winter 1916 - 17. [NOAA]](http://www.wonderquest.com/images/2004-01-23-snowy-trees.jpg)
Q:
Last night (12/29/03) we got a freak snowstorm of five to six inches in about
two hours, which is unusual for this part of Oregon. It was still snowing hard
at about 1 o’clock in the morning when I saw the entire western sky flash
several times a bright green color and then maybe an orange color, too. What
happened? Greg, Corvallis, Oregon A: That’s hard to say but here are some good guesses.
It’s not an aurora, says Joseph Hawkins, electrical engineering professor at the University of Alaska. "It was probably too cloudy," agrees Bob McDavitt MetService Weather Ambassador, New Zealand.
You might have seen lightning, which is well documented in winter storms, says William Winn, Langmuir Laboratory for Atmospheric Research. The colors are unusual but could happen. White lightning can take on various hues when the atmosphere filters out some colors from the original white light.
An exploding power transformer may be the cause. Jack Williams of USA Today once answered a similar question about light flashes during a hurricane.
Peter Black, who has been flying into hurricanes since the 1970s, says transformer failures flare up as a "bright greenish flash followed by a lingering glow." Occasionally, these episodes take on a "reddish cast." He also said the only way to distinguish the transformer failure from lightning was that the transformer display lasts longer, perhaps 10 seconds.
Granted, what you experienced was a heavy snowstorm, not a hurricane. Snow laden tree branches, however, can break and crash into transformers, which then explode.
"I have seen such flashes in Ontario when squirrels crawl into the transformers for shelter and are killed during ice storms," says Keith Heidorn, The Weather Doctor.
The Weather Doctor by Keith Heidorn
(Answered Jan. 23, 2004; updated Oct. 18, 2007)