monthlong

From month +‎ -long.

monthlong (not comparable)

1. Which lasts a month, or approximately so.
   • 2011 January 12, Joel Kirkland, “Australia's Record Rains Squeeze World Coal Supplies as Scientists Study Climate Pattern”, in The New York Times‎^[1]:

     In early December, as rainwaters had started the monthlong process of flooding mines and washing out rail lines, workers lined up before 1 p.m. at an easy-to-miss storefront depot in Mackay.