Ralph Wright, soil moisture specialist with Alberta Agriculture, has released a map showing that overnight temperatures dipped below zero across two large areas on the night of Sept. 11-12
These areas are roughly centred around Edmonton and Grande Prairie. Several stations recorded overnight temperatures that dipped below 0 C, across two large areas; one centred roughly around Edmonton and the other centred roughly around Grande Prairie. Generally a “Killing” frost occurs at or below about -2 C.
Overnight lows appeared to be sustained for at least a couple of hours, with some of stations seeing temperatures sustained near the -2 C degree range. In these areas, wide spread frosts of -2 C, for this time of year, are estimated to occur between once in 10 to once in seven years. Low-lying areas likely saw temperatures lower than what is depicted in this map.