Since moving to the prairies I have learned a new definition for the word "overcast" in reference to the sky conditions. The prairie weather persons' definition of "overcast" is actually "dark"!
O-v-e-r-c-a-s-t on the prairies = DARK!
To date, in my experience with sky conditions, "overcast" has meant light to medium grey clouds partially obscuring the sun for brief periods throughout the day, still allowing for at least a few bright sun's rays to shine to earth even at the most cloudy times, blots and blips and patches of blue sky still visible to the naked eye.
But here it seems to mean that ugly black clouds will fill the entire sky to the point where the exact location of the sun is obscured, blotted out, nearly impossible to discover.
"Overcast" around here means that it appears a giant rain storm is imminent, only the rain never happens.
"Overcast" around here means that all the lights in the house have to be put on even at what should be the sunniest noon time to avoid tripping over throw rugs, or my own big feet, while traipsing about the interior darkness.
"Overcast" here where I live is just a fancy 8 letter word for: DARK!