July is our hottest month, averaging three days annually over 30C (the rest above 25C) with close to 100% humidity and, more importantly, consistent night-time temperatures above 15C for two months. 2003 saw 21 consecutive days above 30C in July alone, 2004 saw none in the entire year, so it is variable. 15C+ makes sleeping uncomfortable though, if you don't have air-conditioning.