Where are the hidden switches?

The description for the Snowblind achievement in EDGE states that you need to find some switches.

Find the six hidden switches in the snow-covered levels in December.

Which levels are the snow-covered ones, and where are the switches?

This thread explains it all pretty well.

Three levels were updated with snow - Normal 1, Bonus 1, and Extended 6. Each of these have two hidden switches.

Here are the locations of the switches for Normal 1:

Switch 1

Switch 2

Here are the switch locations for Bonus 1:

Switch 1

Switch 2

Here are the switch locations for Extended 6:

Switch 1

Switch 2

Finally, this video shows you where to find them all if the pictures were not clear.