Rapid, diurnal, wintertime,cold temperature photochemical ozone production at temperatures as low as -15C has been observed to occur regularly in the rural Upper Green River Basin, Wyoming, USA during sharp temperature inversion events. In these events, hourly average ozone concentrations rise from 10-20 ppb at sunrise to 120 ppb shortly after solar noon across 100s of km² in and near the Jonah-Pinedale Anticline gas field. The ozone concentrations rapidly decrease as the sun sets. These daily photolytic ozone concentrations approach the U.S. Environmental Protection Agency (USEPA) 8-hour average concentration exceedance level of 75 ppb. Violations may result in regulatory curtailment of wintertime production in the gas field that produces at least 17 million m³ yr^-1 (600 mfc) of natural gas, enough to supply the energy needs of 3 million US homes and valued at about U$ 3 billion/yr. Surprisingly, these very high ozone concentrations occur well outside the April to October time of the year which USEPA ozone regulatory measurements are required. Similar geographic and meteorological conditions exist in Canadian and Russian oil and gas fields.