This report describes the historical weather record at the Edmonton/Namao Heliport (Edmonton, Alberta, Canada) during 1981. This station has records back to November 1955.
Edmonton, Alberta has a humid continental climate with warm summers and no dry season. The area within 25 mi of this station is covered by grasslands (56%), croplands (33%), built-up areas (4%), forests (4%), and lakes and rivers (3%)
Daylight saving time (DST) was observed at Edmonton, Alberta during 1981. There were two time changes during 1981:
1981 was not a leap year, so it has 365 days and no February 29th. The first leap year before 1981 was 1980 and the first after was 1984.
The summer and winter solstices and the spring and fall equinoxes mark the passing of the seasons. They fall on nearly the same day each year, with differences of a day or two depending on the year. In 1981 they occurred on:
|Spring Equinox||Friday, 20 March 1981.|
|Summer Solstice||Sunday, 21 June 1981.|
|Fall Equinox||Wednesday, 23 September 1981.|
|Winter Solstice||Monday, 21 December 1981.|
The hottest day of 1981 was August 10, with a high temperature of 91°F. For reference, on that day the average high temperature is 71°F and the high temperature exceeds 81°F only one day in ten. The hottest month of 1981 was August with an average daily high temperature of 77°F.
Relative to the average, the hottest day was September 17. The high temperature that day was 90°F, compared to the average of 62°F, a difference of 28°F. In relative terms the warmest month was March, with an average high temperature of 41°F, compared to an typical value of 32°F.
The longest warm spell was from January 1 to January 28, constituting 28 consecutive days with warmer than average high temperatures. The month of January had the largest fraction of warmer than average days with 87% days with higher than average high temperatures.
The coldest day of 1981 was December 31, with a low temperature of -24°F. For reference, on that day the average low temperature is 5°F and the low temperature drops below -13°F only one day in ten. The coldest month of 1981 was December with an average daily low temperature of 6°F.
Relative to the average, the coldest day was December 31. The low temperature that day was -24°F, compared to the average of 5°F, a difference of 29°F. In relative terms the coldest month was June, with an average low temperature of 46°F, compared to an typical value of 47°F.
The longest cold spell was from June 16 to June 25, constituting 10 consecutive days with cooler than average low temperatures. The month of June had the largest fraction of cooler than average days with 63% days with lower than average low temperatures.
The longest freezing spell was from December 8 to December 19, constituting 12 consecutive days with temperatures strictly below freezing.
The clearest month of 1981 was January, with 10% of days being more clear than cloudy.
The cloudiest month of 1981 was February, with 79% of days being more cloudy than clear. The longest spell of cloudy weather was from November 12 to November 27, constituting 16 consecutive days that were cloudier than they were clear.
This station provides hourly reports of significant weather events at and around the station, but does not report the quantity of precipitation at the station itself. This is common for weather stations located outside of the United States, and for a small subset of stations in the United States that are located at lesser used and smaller airports.
This station reports when significant weather events (including precipitation) are visually observed at or near the station. Such events do not always correspond to measured quantities of liquid equivalent precipitation, such as when the event is near by not at the station, or in the case of solid precipitation that does not melt in the collection basin.
The day in 1981 with the most precipitation observations was January 28. There were 23 hourly weather reports that day (out of a maximum of 24) in which some form of precipitation was observated at or near the station. The month with the most precipitation observations was January, with 128 hourly present weather reports involving some form of precipitation.
As determined by the present weather reports, the longest dry spell was from January 10 to January 24, constituting 15 consecutive days with no observed precipitation. The month with the largest fraction of days without observed precipitation was August, with 77% of days reporting no observed precipitation at all.
The month with the largest fraction of days with at least some observed precipitation was July, with 68% of days reporting some observed precipitation.
In this section we consider only those weather reports that indicate liquid precipitation. For the purposes of this analysis, we include thunderstorms even though some thunderstorms are not accompanied by liquid precipitation.
The month of 1981 with the largest number of those reports was July, with a total of 123 reports. The day with the largest number of those reports was July 7, with a total of 21 reports.
This station reports both when snow is observed to be falling and the measured depth of the snow on the ground. Both are subject to erroneous reports, but the latter is significantly less reliable. Please bear this in mind when reading this section.
In this section we consider hourly weather reports that contain an observation of falling snow. These reports do not necessarily correspond to accumulation.
The first reported snow fall in 1981 was on October 19; the last was on April 12. The month of 1981 with the largest number of those reports was January, with a total of 127 reports. The day with the largest number of those reports was January 28, with a total of 23 reports.
Snow depth on the ground is an optional and inconsistently reported part of standard weather reports. It is rarely reported more often than every six hours, it is often skipped, it is often reported erroneously, and a snow depth of zero is normally not distinguished from a missing report. These issues (particularly the last one) make it hard to collect statistics on snow depth with any confidence. To overcome this issue, we base our statistics on only those reports with present non-zero measurements of snow depth. Reports that fail to mention snow that is present, and reports that do not report snow depth because there is no snow on the ground are excluded because they cannot be distinguished from one another.
The first reported accumulation in 1981 was on November 28. The last day of the snow season with snow reported on the ground was April 13. The day with the deepest snow depth was February 8, with an average snow depth of 7.9" over the course of the day. The longest stretch of time during which there was always snow on the ground was from January 10 to January 25 (16 consecutive days).
Humidity is an important factor in determining how weather conditions feel to a person experiencing them. Hot and humid days feel even hotter than hot and dry days because the high level of water content in humid air discourages the evaporation of sweat from a person's skin.
When reading the graph below, keep in mind that the hottest part of the day tends to be the least humid, so the daily low (brown) traces are more relevant for understanding daytime comfort than the daily high (blue) traces, which typically occur during the night. Applying that observation, the least humid month of 1981 was April with an average daily low humidity of 36%, and the most humid month was January with an average daily low humidity of 68%.
But it is important to keep in mind that humidity does not tell the whole picture and the dew point is often a better measure of how comfortable a person will find a given set of weather conditions. Please see the next section for continued discussion of this point.
Dew point is the temperature below which water vapor will condense into liquid water. It is therefore also related to the rate of evaporation of liquid water. Since the evaporation of sweat is an important cooling mechanism for the human body, the dew point is an important measurement for understanding how dry, comfortable, or humid a given set of weather conditions will feel.
Generally speaking, dew points below 50°F will feel a bit dry to some people, but comfortable to people accustomed to dry conditions; dew points from 50°F to 68°F are fairly comfortable to most people, and dew points above 68°F are increasingly uncomfortable, becoming oppressive around 77°F.
To take some examples, and basing our categorization on the daily high dew point in 1981, January had 31 dry days, no comfortable days, and no humid days; April had 30 dry days, no comfortable days, and no humid days; July had 4 dry days, 27 comfortable days, and no humid days; and October had 31 dry days, no comfortable days, and no humid days.
The highest sustained wind speed was 30 mph, occurring on April 5; the highest daily mean wind speed was 20 mph (April 6); and the highest wind gust speed was 52 mph (June 6).
The windiest month was April, with an average wind speed of 9 mph. The least windy month was August, with an average wind speed of 6 mph.
Visibility is the maximum distance at which a given reference object or light can be clearly discerned. In the United States, visibilities that are greater than or equal to 10 miles are typically reported as 10 miles.
The day of 1981 with the lowest average visibility was November 23, with an average visibility of 0.0 mi. The month with the lowest average visibility was November, with an average visibility of 11.6 mi. With an average visibility of 14.7 mi, the month of June had the highest average visibility.
The cloud ceiling is the altitude of the lowest layer of clouds that are at categorized as broken (mostly cloudy) or overcast (cloudy). If no such cloud layer exists then the ceiling is unlimited and no value is reported.
The day of 1981 with the lowest average cloud ceiling was August 12, with an average cloud ceiling of 49'. The month with the lowest average cloud ceiling was September, with an average cloud ceiling of 9972'. The month of April has the highest average cloud ceiling, with an average cloud ceiling of 16467'.