HOULTON, Maine — Sections of Aroostook County have now been categorized as a drought category D3 — extreme drought — making it one of the driest summers on record for the state. The severe drought status is characterized by low moisture in the soil and lack of widespread rainfall, drying vegetation and low stream flows. Measurements obtained from United States Geological Survey water monitoring stations in Masardis and West Enfield show that water levels in the Aroostook and Penobscot rivers have reached their all-time lowest point during this time of the year, according to Nick Stasulis, data section chief for the USGS.