Every summer the salons fill with women who want to be beach blondes - and every August those same women come back disappointed. Hairdressers have a clear warning: if you get light highlights in June, by mid-August your hair won't be blonde, but yellow and wrecked.

The explanation is simple. Sun, chlorine, seawater and frequent washing naturally lighten the hair all summer long. "If you get lots of blonde highlights in June, by mid-August you'll have hair as yellow as a chick and ruined," warns hairdresser Carlos Ortigosa. His advice runs against instinct: instead of the lightest tone, choose a deeper one.

"Be smart about it - pick a deeper or darker tone than usual and let the summer work its magic," says Ortigosa. Tones with golden, honey, caramel and hazelnut undertones last better than cool blonde shades, because the sun will lighten them further anyway. For the technique he recommends a balayage on the mid-lengths and ends, with a "faked" regrowth, so there's no visible line when the hair grows out on holiday.

Colourists add that colour is only half the story. Complete care - masks, sun protection and rinsing with fresh water right after a swim - is what keeps the hair alive until the end of the season. In other words, beach beauty doesn't come from a single salon visit in June, but from care that lasts as long as the summer itself.