▁square ▁miles ▁( 9 6 7 . 2 9   km 2 ) ▁is ▁land ▁and ▁ 3 . 9 2 ▁square ▁miles ▁( 6 . 3 0   km 2 ) ▁is ▁covered ▁with ▁water . ▁Hart sel ' s ▁elev ation ▁is ▁ 2 , 7 0 2 ▁meters ▁( 8 , 8 6 4 ▁feet ). ▁ ▁Cl imate ▁ ▁According ▁to ▁the ▁Kö ppen ▁climate ▁classification ▁system , ▁Hart sel ▁has ▁a ▁Cold ▁Sem i - ar id ▁climate ▁( BS k ). ▁According ▁to ▁the ▁United ▁States ▁Department ▁of ▁Agricult ure , ▁the ▁Plant ▁Hard iness ▁zone ▁is ▁ 3 b ▁with ▁an ▁average ▁annual ▁extreme ▁minimum ▁temperature ▁of ▁- 3 0 . 7   ° F ▁(- 3 4 . 8   ° C ). ▁ ▁E col ogy ▁ ▁According ▁to ▁the ▁A . ▁W . ▁K uch ler ▁U . S . ▁Pot ential ▁natural ▁veget ation ▁Types , ▁Hart sel ▁would ▁have ▁a ▁Whe at gr ass ▁/ ▁Need le gr ass ▁( 6 6 ) ▁veget ation ▁type ▁and ▁a ▁North ▁M ixed ▁grass ▁pra irie ▁( 7 ) ▁veget ation ▁form . ▁ ▁Dem ograph ics ▁ ▁As ▁of ▁the ▁census ▁of ▁ 2 0 0 0 , ▁the ▁population ▁of ▁Z IP ▁code ▁ 8 0 4 4 9 ▁was ▁ 6 7 7 ▁with ▁ 2 8 4 ▁households . ▁The ▁population ▁density ▁was ▁ 1 . 1 3 ▁per ▁square ▁mile ▁( 1 . 8 1 ▁per ▁km 2