The impact of hydrothermal variability on organic sunflower seed yield in the humid tropical region of Nigeria was studied between 2001 and 2008 using rainfall and temperature as proxies for climate variability. The test variety was 'Funtua' a local adapted open pollinated and late maturing sunflower variety. Rainfall amount during the period of study compared favorably with the long-term mean (25 years). September recorded adequate amount of rain throughout the period of study except in 2002. Sum of effective temperature and growing degree days (GDD) ranged between 1907.1 and 2440.3°C and 2435.2 and 3634.3°C and appeared adequate for the production of organic sunflower in the region. Sunflower seed yield obtained between 2001 and 2005 ranged between 1.03 and 1.26 t/ha and were superior to the Nigerian average of 1.00 t/ha African average of 0.81 t/ha and a little below the world average of 1.52 t/ha. Grain yield however declined in 2006 and thereafter remained below 1.0 t/ha till 2008. Nevertheless it could be concluded that despite the global increase in climatic variability a good yield of sunflower is still possible in the humid tropical region.