Prices at the pump are heading up across Arizona. Triple-A Arizona says gas prices have shot up nearly six-cents a gallon on average since last week to $2.51 a gallon. In Flagstaff, the average price of gas is up just over three-cents to $2.65 a gallon. However, some stations are selling gas for $2.47 and lower. In Prescott, gas is up almost two-cents a gallon on average to $2.71 a gallon. However, some stations are selling gas for $2.52 and lower. Officials say several factors are leading to the price hike. Higher demand, lower supply, refinery maintenance and an unstable oil market are all leading to the spike.