Figure 3: (a) Annual number of consecutive days 18˚C, Toronto. Bars indicate the number of consecutive days per year that temperatures 18˚C. A trendline (solid line) shows the 10-year moving average for the data. The trendline suggests that in the last few years, we have begun to experience sufficiently prolonged summer warm periods to support parasite replication and malaria transmission potential. In 2002 and 2005, the number of days above 18˚C was sufficient to support 2 cycles of P. vivax replication. These data should be considered conservative since each degree-day 18˚C will reduce the remaining time required for parasite replication. Additionally, breaks in consecutive warm days 18˚C do not necessarily prohibit continued development once temperatures rise [35]. Source of climate data: Environment Canada [46]. (b) Annual number of consecutive days 18˚C projected for 2010–2099, Chatham (ON). Bars indicate the number of consecutive days per year that temperatures are projected to reach or exceed 18°C. Error bars indicate the range of values during each time period. The climate change projections were obtained from interpolation (for Chatham, Ontario) of output from the CGCM2 (Canadian Coupled Global Climate Model 2) [47] that were downscaled using LARS-WG stochastic weather generator. LARS-WG was calibrated with 30 years of daily weather observations at Chatham (and its predecessors) obtained from the Environment Canada database. The output used here was obtained using emissions scenario A2 (business as usual). The data and methodology used here are the same as described in Ogden et al. [49]. The projected trend shown here indicates increasingly extended summer warm periods sufficient to support multiple parasite replication cycles.