Markets are best for sellers when there is the highest amount of demand in proportion to the least amount of supply. I am searching within the following map area and only looking at detached single family homes.

 

First I want to see if there is a trend as to if certain months have frequent low prices in the market, and if certain months have frequent high prices in the market. Here is a graph of historic average sales prices by month. 

Keep in mind that sales occur approximately 30 days after the listing period. So, for instance, if January has a high or low point, this would likely be representative of homes that were listed in November and December of the previous year. 

Low points include Jan 2013, Feb 2013, March 2013, Aug 2013, Oct 2013, April 2014, November 2014, April 2015, Oct 2015, Dec 2015, April 2016, Dec 2016, Feb 2017, Oct 2017, April 2018. I feel like April, October, & December have the most low points. Current theory worst months to list March, September, November.

High points include Dec 2012, Jun 2013, Jan 2014, May 2014, Sep 2014, Mar 2015, May 2015, Aug 2015, Feb 2016, May 2016, June 2016, Nov 2016, Jan 2017, Mar 2017, Sep 2017, Feb 2018. I feel like May & February have the highest frequency of high points. Current theory: best months to list April, January. 

Second, I want to see which months appear to have the highest and lowest days on market.

The months that have the highest days on market are March 2012, Oct 2012, Nov 2012, Dec 2012, Feb 2014, Oct 2014, Dec 2014, March 2016, Oct 2016, Dec 2016, Mar 2017, April 2017, Sep 2017, Dec 2017. December and October seem to have the highest days on market with the most frequency.

The months that have the lowest days on market are June 2012, June 2013, September 2013, March 2014, Oct 2014, April 2016, May 2016, April, 2017, June 2017, Nov 2017, March 2018. April seems to have the highest frequency.

Finally, which months have the highest and lowest months of inventory?

It's hard to get much from this.

In conclusion I would list mid March to the end of March in my opinion.