Eighty six mixed‐parity Large White sows were used to determine the effect of three diets : a normal protein diet (NP), a low protein diet (LP) and a NP diet (NP+) supplemented with essential AA, on 28‐d lactation performance under humid tropical climatic conditions (Guadeloupe) in two seasons. The NP and LP diets supplied the same level of standardized digestible Lys (i.e., 0.80 g/MJ of NE) and the NP+ diet supplied 0.95 g/MJ of NE. No interaction between season and diet composition was noted. The ADFI was lower (P < 0.05) in the hot season (i.e., 3.69 vs. 4.72 kg/d). The ADFI tended to be higher with the LP and NP+ diets when compared with the NP treatment (i.e., +10%, P = 0.08). Milk production was not affected by dietary treatments but was affected by season (8.1 vs. 6.8 kg/d, for cool and hot seasons, respectively; P < 0.01). The sows fed LP and NP+ diets tended to show lower backfat thickness losses (3.3 and 3.8 mm, respectively; P > 0.08). In conclusion, the hot season in humid tropical climates has a pronounced negative impact on performance of lactating sows which can be attenuated with diets with low CP content or supplemented with essential AA.