Certain roses are more fragrant at hot temp, like Double Delight and Chrysler Imperial. In cold weather, those scents went downhill. In contrast, Austin roses smell best at cool temp. In hot temp, my Austin Scepter'd Isle smells like dirty-socks, and Radio Times & Wise Portia lose 1/2 of its scent. But the French Romantica roses are consistently fragrant regardless of temp.