Warmer temperatures and school holidays helped U.K. e-retailers boost sales by 16% year over year in April, according to the latest report from business and technology consultancy Capgemini and U.K. e-retail association Interactive Media in Retail Group (IMRG). To date, that puts the average annual growth rate of U.K. e-commerce at 15%, beating IMRG’s initial 2013 forecast of 12%, says the group’s chief information officer Tina Spooner.

The report provided no spending amounts.

Web-only retailers fared best in April, with sales up 20% year over year compared with a sales increase of 14% year over year for multichannel retailers, the report—the IMRG Capgemini E-retail Sales Index—says. That mirrors a trend in last year’s figures when both types of merchants tracked similar sales during the winter holidays, then diverged. The report suggests the likely causes include increasing consumer confidence about online purchasing and more use of shopping technologies like mobile devices and social media, which web-only retailers tend to introduce first.

“With the holiday period [Easter] falling at the start of April and warm weather following in the second half, we have seen uplifts in holidays, home and garden, alcohol and apparel driving the index,” says Chris Webster, vice president, head of retail technology and consulting at Capgemini.

U.K. e-retailers sold 19% more beer, wine and spirits in April than in the same month last year, the report says. Their online travel sales increased by 16% year over year and by 2% from March to April, marking the first time the category has grown between those months since IMRG and Capgemini began tracking it in 2009, they say. The two groups did not immediately disclose the growth rates for home and garden or apparel web sales.

Additionally, while mobile sales in the United Kingdom continue to increase with vigor, their growth rate is slowing, IMRG and Capgemini say. U.K. m-commerce, excluding travel sales, grew 131% year over year in April, down from 243% year over year in March, the two groups say. However, they say the lower percentage increase is expected as mobile shopping becomes widespread.

Including travel sales, U.K. m-commerce in April jumped 172% year over year, with mobile travel sales alone up 41% year over year, says Oliver Ripley, mobile products manager at London based e-commerce platform and analytics provider eCommera Inc.“Travel remains one of the key growth areas for mobile commerce as, by definition, travellers are away from home when abroad yet still want to have access to services that not only allow them to plan trips but also to help them enjoy their destinations,” he says. Internet retailers focused on travel should consider what mobile functionality they can offer to take advantage of this growth period, he says.