It should be no surprise that buying activity (contracts being signed) slows down over the Winter.  As shown above -- an average of 75 buyers sign contracts in January, which then increases a bit, to 87, in February, and then makes an even larger jump in March to an average of 134/month.

So, we're going to say the March is when we first seem a big jump in buyer activity.  For that reason, many sellers wait until March (or even April) to put their homes on the market -- though the Spring market brings more competition from other sellers in addition to meaning that we'll start to see more buyers.

Of note -- so far there have been 19 contracts signed in 2019 -- so still a ways to go to get to that average of 75 in January.