BARRIE, ONT. -- Mother Nature is slowly opening the 'dome'; the 'heat dome,' that is.

The 'heat dome' is a ridge of high pressure in the upper atmosphere that helps seal in hot air.

This "Dome" has kept sweltering temperatures stationary right across south-central Ontario for the past five days.

Humidex highs of 40+ degrees are almost becoming routine.

The oppressive heat has some areas of the province experiencing poor air quality.

But relief from the heat is on the way. A low-pressure system arriving later today will push the stagnant high-pressure system away, opening the 'heat dome.'

The cold-front could come with potentially intense showers and severe thunderstorms.

The intense humidity should lift, but not necessarily the heat, once the 'dome' opens. Temperature highs near 30 degrees should remain with cooler temps near the water.

The cooler conditions aren't likely to last; the 'heat dome' could seal up again for August.