Cotton (Gossypium hirsutum L.) grown in the Mississippi River Delta is generally planted in cool and wet weather conditions that lead to slow germination, uneven emergence, and poor root growth. The optimum temperature for cotton root development is reported to be 28°C. The base temperature for plant growth is generally accepted as 15.5°C and the minimum temperature for cotton germination to be near 12°C. However, low temperature during the initial growth stage is a problem that affects all cotton cultivars produced across the Mississippi Delta. This research showed that root growth response to temperature exists among the four diverse cultivars culminating in various growth patterns to the temperature regimes. Cultivar Stoneville 4892BR had the most sizeable root growth over the entire range of temperature regimes while Tamcot Sphinx had the most predictable growth pattern with peak growth at 15°C to 35°C. Root dry weight was proportional to root length among cultivars. Cotyledon dry weight exhibited no association with root length or root dry weight. Genotypic differences for root development between cotton cultivars can be examined to find a cultivar able to withstand cool temperatures and produce a vigorous root system for a more healthy plant and yield stabilization.