Dulles airport delays and cancellations?

Hi I am traveling from South Texas to Namibia Africa Feb 20th and the most economic flight I can find changes planes in Dulles. What is the likely hood of my flight being delayed or canceled due to snowy weather or ice around late Feb. I know south Texas can get cold around that time but we don't get snow. This trip has been a long time in the planning I know another flight that goes through Houston but is almost $300 more. any help would be appreciated thanks