In Australia, rainbow trout are limited to the cooler temperate waters in the south-east and south-west. Government stocking supports much of the recreational fishery throughout this range. A key limiting factor for this reduced distribution are the high summer temperatures experienced in Australia. In contrast, Gaden Trout Hatchery at Jindabyne experiences some of the coldest winter weather in Australia, and the associated low water temperatures (<4ºC) slow the development of embryos and early growth of rainbow trout, limiting production. As a result, rainbow trout fingerlings are not stocked until the end of summer, when water levels are at their lowest and temperatures at their highest. This study examines the potential benefits for the fishery of artificially warming hatchery water to improve development and early growth and to optimise the fingerlings return when released. Rainbow trout raised in warmer water were typically ~20% larger than those hatched and raised in river water. In addition, return rates to the spawn run in the Thredbo River and angler catches in Lake Jindabyne for rainbow trout were higher for the fish raised in warmer waters than those grown in ambient river water. Rainbow trout raised in warmer water also maintained a larger average length and returned to the spawn run a year earlier than fish raised in river water. However, fish raised in warmer water appeared to exit the fishery within 3 years. The outcomes of this research will be used to develop adaptive stocking strategies in NSW.