Figure 2

The monthly mean air temperature, total rainfall, mean relative humidity, and the monthly distribution of chickenpox cases in Princess Margaret Hospital from 2004 to 2008*. (* The units for the monthly mean temperature and monthly rainfall are degrees Celsius and millimeters respectively. For the relative humidity, 0.75 refers to 75% relative humidity, and 0.80 refers to 80% relative humidity, etc. For the dates, 2004-06 denotes June 2004, and 2004-12 denotes December 2004, and so on).