As the online advertising division of Media Initiatives Group, eType aims to increase revenues and boost awareness of the site, which has 1.5 million monthly unique users.
Rob Gay, managing director of eType, said: "We will work alongside weather.co.uk to build the site's profile with advertisers by pitching standard ad formats, as well as specific campaigns and sponsorships that complement the site's content and appeal to users."
Portals, including Yahoo! and Orange, have implemented weather.co.uk's technology to provide users with up-to-the-minute weather conditions and forecasts from around the world. Other eType clients include hi5, The Eggnetwork, Excite, Miniclip and Visit London.