Costa has seen like-for-like sales (LFLS) increase by 7.3% in the 11 weeks to 14 August.
The coffee giant grew overall UK sales by 17.8% in the same period, and opened 76 new stores.
The company said these positive results were aided by weak comparatives from last year’s exceptionally warm weather in July.
The brand, owned by Whitbread, has also revealed its new coffee blends; the first for the coffee shop in almost 50 years.
Andy Harrison, chief executive of Whitbread said: “In early September, Costa launched Old Paradise Street Limited Roast, which is a new range of limited edition roast blends.
“This will provide coffee lovers with a wider choice of great tasting coffee, in addition to Costa’s Mocha Italia, from the UK’s favourite coffee shop.”
The Costa brand also hopes to open around 300 new stores and 600 Costa Express units in the full year.
Worldwide, Costa grew system sales by 15.3% to £6bn. Within this, its franchise system sales grew by 14.2% to 2.26bn.