The Barclay's Municipal Bonds Index is up around 4% year-to-date, yet it has been drifting lower as bonds have sold off in the past month sending yields higher. John Dillon, managing director at Morgan Stanley Wealth Management (MS) - Get Report , said investors need not panic because munis will hold onto their gains. In the interim, Dillon said he views the weakness as a buying opportunity. Based on the historic seasonality of the muni market and according to ICE Data Services, Dillon expects the amount of bond redemptions to decline significantly during September, October and November, which is actually expected to be the lowest month of this year. A few months ago Puerto Rico's problems were on the tip of every muni investor's tongue, but lately it has been very quiet on the Puerto Rico front. Dillon said the PROMESA bill put before the President by Congress, which was passed and signed into law before one of the largest defaults, actually has had a "mildly positive impact on the overall market" even though the defaults continued.