As the weather heats up and picnics, summer parties, holidays and lazy afternoons are with us, heavy chewy reds with a lot of tannins should not be your wine pick as Jancis Robinson reminds us in her Saturday column It’s time for reds to feel the chill (FT Weekend).
Amongst her recommendations are a Te Mata Woodthorpe Gamay Noir 2006 from New Zealand which besides lush fruit has the additional distinction of bearing the New Zealand Sustainable Winegrowing Stamp. 
From the less traveled Italian appellations she picked the Donnafugata Sedara Nero d’Avola 2005 from Sicily whose label illustrates this story.
I would suggest that a nice Rosé lightly chilled such as a good Bandol can be a crowd pleaser.
Other wines of Summer: Mesta Tempranillo, juicy and light