Nov 9 (Reuters) - Italian shoemaker Geox slightly lowered its full-year sales guidance for a second time on Thursday, after reporting that preliminary sales had risen 4.1% in the first nine months of the year from the same period of 2022.

The maker of breathable, waterproof footwear now sees full-year sales growth in the low to mid single digits at constant exchange rates, compared to previous guidance of between 4% and 6% year-on-year.

However, it said it expected its full-year gross margin to increase by 250-300 basis points, up from a previous forecast of 220-240 bps.

Geox said the lower sales guidance reflected "a slowdown in sales performance in May and September due to decidedly abnormal weather conditions".

Changing weather trends would force the firm to rely more heavily on best selling products and marketing, Geox Chief Executive Livio Libralesso told analysts, without giving further details.

The group appointed Spanish actress Penelope Cruz as a global ambassador in September in a push to unlock the potential of the women's market.

The firm also appointed Andrea Maldi as chief financial officer from Dec. 4 as part of a management revamp, Libralesso added.

Geox's total sales were 582 million euros ($623.3 million) in the January-September period, from 569.1 million euros a year earlier. ($1 = 0.9338 euros) (Reporting by Alessandro Parodi, editing by Kirsten Donovan)