Gained MMR out of no where

So I check op.gg every once in a while just to see how my mmr is doing and it usually goes up or down 3 or 4 points every couple of days. It usually hung around 1550. Today when I checked though, it was 1805. I'm just wondering why my MMR would shoot up 250 points without playing ranked for a couple of weeks. I get that MMR is always changing, but 250 seemed drastic and I my friends MMRs stayed relatively the same. Any thoughts on this?