Unilever is launching a weather-forecasting service this week to help retailers plan ice cream purchasing.

The model correlates average weekly temperatures and sunshine hours with sales data for the past three years, enabling the company to make an accurate prediction of demand using the weather forecast.

The system would protect retailers from both over and under-stocking, said Vanda Noakes, senior category and market insight manager. The move follows last year's 1.5% slump in ice-cream category sales to £605.4m [TNS 52 w/e 4 November 2007].

The launch came as Unilever revealed sales of the £77m Magnum brand had "soared" in the past week due to the weather. Multipack sales of the brand, currently fronted by Desperate Housewives star Eva Longoria, were up 36.6% year-on-year, with more than 23 million Magnums sold in 2008 [IRI].