If it would help, I track sales of 3 BR, 2+ bath homes in Meridian between 1300 and 1900 square feet and less than 15 years old. Average Days on Market for this specific subset was 29 days for homes closed in December and 39 days for homes closed in November. You can read the full update and download a copy of the report with statistics back to 2004 at the web reference below.
Brian is right on the mark when it comes to his information. There are so many determining factors when figuring an average days on the market in an area as large as Meridian with just 3 bedrooms as the only other criteria. Meridian has homes that are very old to under construction which would figure into the average. There are also "contingent short sales" which affect the numbers. His figure of 52 days is probably as good as you are going to get on this type of criteria. If you want to really have a good idea of what you are looking at, you would need to supply age, location, size and condition.
Obviously there are going to be a lot of varying factors; size, age, neighborhood, condition. You would want to take these and more into consideration when coming up with an accurate number. Right now the 3 month average based on 3 bedroom homes sold in all of Meridian is 52 days on market.