Cool will likely rule for August 2013.

Cooler than normal temperatures have ended July and will continue into August thanks to an upper level trough over the Great Lakes region. This trough effectively blocks hot and humid air from making it's way northwards.
Several computer models are supporting this cooler trend to continue well into August and perhaps into September.
The CFS or Climate Forecast System is a model that targets specific months given the past state and forecasted state of the atmosphere as well as a multitude of other parameters used in the models calculations.
The graphic below is centred on August and shows the temperature departures from the climatological normal across North America. This map has taken the past 14 days model runs, 4 times daily and averaged them to get the output you see below.

The extended version of this model which goes out 45 days has the same area of below normal temps through to September 15th...

The Canadian model temperature departure shows a huge area of below normal temperatures over the next 10 days....

Temperature departures over 2 are considered significant.... this is showing nearly -5 degrees departure over Southern Ontario.

Here is another look at the Canadian GEM (Global Environmental Multiscale) model which shows the a 7 day average from August 4th through 11th (This model only goes out 10 days).

The GFS (Global Forecast System) which is the main American model is showing that below normal area over the region through to August 17th. (This model goes out 16 days)

I should mention that Im not a big fan of the CFS Model (Graphic at the top of this blog)... however several other models are supporting this cool trend over the area and the CFS has continually shown cooler than normal temperatures on each run over the past few weeks. This tells me the model is showing more confidence in it's output.

With that being said, and several other models showing the same trend, you can bet we will be in for a stretch of below seasonal temperatures for the next while. There will be some warmer days... but on average it looks like we are in for a cooler than normal August. Normal high temperatures around the region are about 27 degrees right now, but will slowly begin to drop through the month to near 24 by the end of August.