BACKGROUND Iodine deficiency is a public health problem in many developing countries where pregnant women and children are the more susceptible populations. OBJECTIVE To evaluate the association of iodine nutritional status with the weather, availability of iodine in salt, and degree of social exclusion in preschool children of the state of Hidalgo, Mexico. METHODS Cross-sectional study in 1,333 children < 5 years; in these, urinary iodine and iodine in the salt was measured, and annual average of humidity, type of location and degree of social marginalization in the localities where they lived was recorded. RESULTS 24.5% of children evaluated had < 100 µg/l of urinary iodine excretion, and 28.6% of salt samples contained < 20 ppm of iodine; iodine urine average of wet weather children was lower (209.09 ± 6.8 µg/l) than in dry climates (274.7 ± 5.86 µg/l; p < 0.05); the iodine content of salt in children living communities with high levels of marginalization was less than with low marginalization (23.5 ± 1.2 and 32.9 ± 2.7 ppm, respectively; p < 0.01). CONCLUSIONS The humidity and the degree of social marginalization of the locations were associated with lower iodine content of salt and urinary iodine in children evaluated.