Daytime highs will continue to sit in the low to mid-30s with lows in the mid-to-high teens across portions of western Canada. Orange and yellow-level heat warnings have been issued from eastern Alberta to the eastern border of Manitoba due to the elevated potential for heat-related illnesses. In their warnings, Environment and Climate Change Canada (ECCC) included reminders for people and animals to stay hydrated, take breaks from the heat and look for signs of heat stress, which may include headache, nausea, dizziness, thirst, dark urine and intense fatigue. Lack of sweat, confusion, high body temperature, fainting and unconsciousness are also common signs of heat-related stress. The main weather-maker is an anchored ridge of high-pressure known as an Omega Block – so named for the shape that is formed when two low pressure systems (with their counterclockwise rotation) sit southeast and southwest of a strong ridge of high pressure (that contains a clockwise rotation). The opposing rotations inhibit the movement of the ridge, so warm air persistently funnels in under the high creating a “heat dome” and often results in multiple days of extreme temperatures. This is the same synoptic setup that was in place over western North America in June and July 2021. Heat like this can be especially dangerous in areas where residents are not acclimated to those types of temperatures and/or where air-conditioning is not common. The physical strain is especially dangerous for vulnerable individuals. The national weather agency advises people to pay particular attention to individuals that can experience earlier or more severe effects from heat, including infants, children, seniors and individuals with pre-existing lung, heart, kidney, nervous system, mental health or diabetic conditions, outdoor workers, as well as those who are socially isolated. Even for people who are not considered at-risk, the toll of existing in this kind of unusual heat is concerning. When the human body is forced to exist in an environment that is close to or exceeds our normal core temperature, all of the body’s internal systems are forced to work harder. These above-seasonal temperatures will continue into Friday before a major shift in the weather pattern occurs. A multi-day rain event will initiate on Friday in portions of southern British Columbia with heavy rain likely to start in Alberta on Saturday. Some areas of the province will see more than 50-millimetres of rain over a three-day period. Calgary is likely to record at least that amount – if not more. This will be a dramatic change, as the province flips from a higher wildfire risk and very dry surfaces to an intense amount of rain over a short period of time. If this does play out and that system gets stuck in the foothills and across central and southern Alberta, there will almost certainly be localized flooding as the ground rapidly becomes saturated and water is forced to run-off. Daytime highs will also drop significantly over the weekend – going from 28 C in Calgary on Friday to 18 C on Saturday and 11 C by Sunday. Overnight lows will be cold enough in some higher elevation areas that mixed precipitation is possible. Before the rain event, areas west of the heat warnings experience weather conditions on Thursday that will likely be similar to Tuesday and Wednesday, with scattered showers and isolated thunderstorms possible. There will be a mix of sun and cloud, light to moderate wind, and temperatures about 10-degrees warmer than average.
