“Summer & Winter Solstices?” Nope
You might guess that the most brilliantly sunny time of year in Minnesota is the Summer solstice in late June, when the sun is at its highest and the days are longest (the sun actually sets at 9:03 p.m. on June 21, but dusk lingers till almost 10 p.m.).
Similarly, it stands to reason that the darkest time of year is exactly six months later, December 21, when the 
sun and daylight hours are at their nadir.
Wrong, on both counts.
At least to this long-time Minnesotan (interrupted by stints in the Bay Area and Manhattan), the correct answers are: “November” and “March” — albeit with an asterisk.
*Wild Card: Snow Cover
So, the reason early November can feel gloomier than late December locally is because of (reflective) snow cover: brown terrain is darker than white (presumably snow-covered) ground.
That is, assuming there’s snow in late December — true about +80% of the time in the Twin Cities.
Now, fast forward four months or so, to mid-March.
Combine an especially snowy Winter and a late-arriving Spring, and all that reflective snow brilliantly mirrors a surprisingly strong sun.
The only catch: what I’ll call “Pre-Spring Glare” is short-lived, because the relatively strong sun and thawing temps burn thru the snow cover quickly, returning things to a late Fall brown.
At least for another 6-8 weeks or so . . .
Subjective Component
Psychologists can supply another reason why November feels darker than December, and March brighter than June: people habituate (acclimate) to their environment.
Translation: perception of light and dark is subjective.
So, in early Winter (yup, sometime in November locally), Minnesotans are still adjusting to newly-shortened daylight.
Conversely, in March, they’re just emerging from what can feel like a months-long dark cave.
See also, “Minnesota’s Four Seasons.
