The driest Sept in MDT history is .65 in 1986. Driest month all together is .02 in October 1924. MDT has .16 for the month right now with a good chance to be going into the final week to 10 days with a shot at a new record for the month.
Of interest, the .65 record for September is the second highest low point for any month behind .78 in July 1955. Every other month has at least one below .65.