nippy
     adj : pleasantly cold and invigorating; "crisp clear nights and
           frosty mornings"; "a nipping wind"; "a nippy fall day";
           "snappy weather"; (`parky' is a British term) [syn: {crisp},
            {frosty}, {nipping}, {snappy}, {parky}]
     [also: {nippiest}, {nippier}]
Source: WordNet® 2.0