A multiyear research (1998 to 2006) was undertaken with the goal of developing field management tools to improve the productivity of ‘Hass’ avocado orchards in the semiwarm climate of Nayarit. The objectives were: a) to quantify the effect of ambient temperature on floral development of ‘Hass’, and b) to develop and validate prediction models to prognosticate critical stages of floral phenology. Floral development of ‘Hass’ was related to ambient temperature and mathematically modeled. Floral development on shoots of the winter flush was correlated to chilling days accumulated (CDA) at temperatures £ 21 °C, as well as the accumulated intervals between daily maximum and minimum temperatures (ACINT). In the case of summer flush shoots, they were associated to CDA with temperatures £ 19 °C, £ 20 °C and the ACINT. Two floral development prediction models ere obtained for winter shoots, winterCDA £ 21 (R2 = 0.99) and winterACINT (R2 = 0.96). In the case of summer flush shoots three prediction models were developed, summerCDA £ 19, summerCDA £ 20 and summerINTAC, all of them with R2 = 0.99.

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