Rainwater from hurricanes Pauline and Nora was sampled for chemical analysis at the Pacific Coast of Mexico. Rainwater sampling under extreme conditions presents a unique opportunity to study oceanic rain chemical composition. An excess sulphate forumla as low as 0% was measured near the centre of hurricane Pauline in Huatulco Bays. Another remarkable result was obtained in another rainwater sample of Pauline rain bands with a total forumla concentration below the detection limit. Also, Na+ and Cl concentrations were extremely low (0.02 and 0.025 mg L–1, respectively). The explanation of these results is also presented. Some light rains were also collected in Tapachula while Pauline was severely affecting Huatulco Bays. Only rainwater samples from hurricane Nora outer rain bands were sampled in Manzanillo, where it was interesting to evaluate the profound impact that a single power plant had on the chemical composition of hurricane Nora rains. Excess sulphate did not correlate with Mg2+ in Huatulco Bays and Manzanillo. However, it correlated with Mg2+ in Tapachula, even though this town is located 27 km from the coast. A further oxidation of organic sulphur containing compounds combined with a simultaneous transport of sea spray inland is proposed to explain this correlation.

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