The ads, breaking in mid-June for a four-week burst, were created by Fallon.
Set to run on crosstrack poster sites on the London Underground and selected UK city poster sites, the work shows people enjoying the overcast weather while sipping on Starbucks Frappucinos in a bid to target affluent, urban coffee drinkers during the summer.
The new strapline, "Instant summer free with every Frappucino", builds on the success of last year's "Summer's back - time to drink Frappucino" campaign.
One execution shows a girl stretching out to read in a damp sandpit despite the looming clouds and another shows a man sitting at the roadside with his trousers rolled up and his feet in a puddle.
The final execution shows a tie-clad man reclining on his desk on a pillow of old newspapers, as he sunbathes under the rays of his anglepoise lamp.
Starbucks' marketing director, Cathy Heseltine, said: "We're continuing to position Frappucino as a central part of enjoying the British summertime.
The idea that the drink transports you to your own summer experience whatever your environment taps into a real truth of the British - our sheer determination to enjoy a summer, whatever the weather."
Media planning and buying is through Manning Gottlieb OMD. The campaign was written by Andy Mcleod and art directed by Richard Flintham. The photographer was Steen Sunderland, while James Townsend worked on typography and design.