London, Aug 11 : Ice cream makers have seen their sales double this week as the heatwave sweeping across Britain has fuelled a surge in demand. With the Meteorological Office issuing an extreme weather warning from Thursday onwards with highs above 30 degrees Celsius, supermarkets are gearing up for a mammoth weekend, reports dpa news agency. However, smaller businesses are already struggling to keep up, with at least one family-owned company working longer hours to keep orders flowing. A spokeswoman for Mrs Dowsons Ice Cream said: "We've been really busy with orders... a week like this with the heatwave, I'd say they've definitely doubled" The manufacturer has seen visitors flocking to its farm shop, which it runs from Blackburn, Lancashire, along with a rise in demand from wholesale customers. "The ice-cream parlour on the site definitely gets busier on hotter days," the spokeswoman continued. "In terms of wholesale customers, you get a lot of customers calling last minute, saying 'we're really busy with the weather, can we place last-minute orders?'" Its traditional flavours have proven popular this week, but in a sign of Britons branching out into more experimental choices, so has its black cherry amaretto and peardrop. Similarly, Waitrose ice cream buyer Joe Sharkey said its No 1 Colombian Coffee brand had proved a customer favourite over the heatwave. Mrs Dowsons monitors Met Office heat warnings as a gauge of demand, and has fortified its supply chain for when temperatures soar later this week. "We're definitely prepared when it comes to heatwaves like this with drivers and vans and everything," the spokeswoman said. However, members of one family business are having to work "longer hours" to cope with the orders mounting from wholesale customers. Julia Lewis, of Chester-based L Lewis, said: "It's just an escalation of getting busier, as people are running out of stocks and wanting more supply. "They've come to the stage where they need replenishing quicker. There's more stock going and there's more orders." The Met Office has issued an amber heat warning running between Thursday and Sunday, which could see temperatures peak at 36 degrees Celsius across southern England and eastern Wales. Supermarkets believe this will fuel demand even further, with Sainsbury's forecasting a 120 per cent rise in sales of ice cream cones. /IANS