Sweden basically did a lockdown - it just wasn't state-mandated.
If you look at the mobility data [1], you'll see that Sweden followed a very similar trend to its neighbors, and actually maintained lower mobility after other state-mandated lockdowns let up.
Either way, using Stockholm as the geographical reference point the chosen point correlates against dark cold Januari/Februari with average temperatures of -1°C and 7-8 hours of twilight. Considering that keeping the relative number below at the height of summer is quite impressive.