Four years ago, nearly 4,000 gay couples were married in San Francisco. Within months, their unions had been annulled by the California supreme court.

But starting this afternoon, many of those same couples and thousands more are expected to take advantage of the court's latest ruling permitting same-sex marriage to become "spouses for life".

At 5.01pm today, barring further legal challenges, the court's ruling is due to come into force. Several counties and cities planned to keep their clerk's offices open late today to officiate the first ceremonies.

San Francisco Mayor Gavin Newsome, who jumped the gun four years ago by deciding to issue marriage licences to same-sex couples, will again officiate at a ceremony at the city hall.

His first act will be to marry the same couple he first married four years ago, Phyllis Lyon, 84, and Del Martin, 87, a lesbian couple who have been together for 55 years.

More than 600 same-sex couples have booked ceremonies at the city hall over the following 10 days, with 165 scheduled for tomorrow.

Palm Springs has a marriage festival set for June 21, with the city's gay mayor officiating.

In anticipation of a rush of marriage ceremonies, 100 people have been deputised in Los Angeles over the past two weeks to allow them to perform marriage ceremonies, as have 50 in San Diego and 200 in San Francisco.

"We're expecting a crush of newlyweds," said Mayor Jeffrey Prang of West Hollywood, which plans to deputise five city council members.

The ceremonies place California at the forefront of a nationwide move expected to attract thousands of couples from across the country.

Gay marriage has been legal in Massachusetts for the last four years, but only to residents of the state. California promises to honour gay brides and grooms from anywhere.

The numbers are impressive. In a report issued this month, the University of Southern California's Williams Institute estimated that extending marriage to gays and lesbians would boost state revenues by more than $63m.

The study anticipates that about half of the state's 102,000 registered same-sex couples will marry in California in the next three years; it also predicts that more than 60,000 same-sex couples will come from other states to marry.

They will spend some $683m, helping to create more than 2,000 jobs and generating $55m in state and local taxes. Marriage licence fees alone will bring in $8.8m.

Accordingly, hoteliers, wedding planners, florists and jewellers are preparing for what they hope will be a rush of couples, leading some to dub the coming months the "new summer of love".

California's state tourism commission lists hotels and estates from the vineyards of the Napa Valley in northern California to the scorched desert of Palm Springs offering gay marriage packages.

A Travel Industry Association survey found that four of the top 15 travel destinations in the US for gay couples are in California. The fabled pink dollar – gay men spend an average $800 per trip, compared to single straight men's $540 – means that businesses are looking forward to an influx of "dinks" (double income, no kids).

But if the experience in Massachusetts is a guide, after the euphoria of legalisation, gay marriage in California could well settle down to be very similar to straight marriage.

More than half of the 10,500 gay marriages in Massachusetts over the last four years took place in the first six months after legalisation. In the first eight months of 2007, just 867 same-sex couples were married in the state.

And those couples that do get married find that they face many of the same pressures familiar to heterosexual couples, with separations, divorces and disputes over child custody and prenuptial agreements abounding.

Most famously, the lesbian couple that were the lead plaintiffs in the case that brought about the change of law in Massachusetts have since split up.

Research has also shown that marriage appeals more to older same-sex couples. Half of straight people marrying are under 30, while a third of same-sex couples are in their 40s.

But amidst all the nuptial bliss, there is the possibility that the latest round of gay marriages could be as short-lived as the last.

In November, California voters are due to decide whether to approve a ballot proposition top revise the state's constitution to define marriage as a union "between a man and a woman".