Early Toronto Temperatures

Kenneth A. Devine

Aurora, ON, Canada

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Editor’s Note:

The purpose of “Field Notes” is to provide an opportunity for scientists and others involved with research to record first hand accounts of their research with emphasis on the apparatus employed  — purpose built or commercially acquired.  Part of our objective is to learn about the frustrations as well as the successes of using the apparatus that would not be immediately obvious to our readers and which is rarely addressed in scientific journals.  Ken, as a meteorologist and historian of the discipline, is in a position to convey a perspective on the preserved data he provides here and in a subject area that is relevant to the discussion of global climate change. He includes factors of which non specialists analyzing temperature data series may not be aware, e.g. variations of temperatures due to contraction of the glass, change in volume of alcoholic liquid, etc.



While weather observations within the University of Toronto property began at the Toronto Magnetic and Meteorological Observatory in September 1840, 1.4 km to the south, Reverend Charles Dade had taken temperature readings at Upper Canada College (UCC) starting in January 1831 and continued until October 1838.  UCC was located at that time on the north side of Russell Square, an area bounded by King, John, Newgate (now Adelaide) and Graves (now Simcoe) Streets.  Presently this area is directly north of Roy Thomson Hall in the entertainment district of Toronto.  UCC moved north to its present location on Avenue Road in 1891.  Officially Toronto was called York until 1834.

Figure 1 (Spendlove, 1958) shows the UCC buildings which backed onto the south side of Newgate Street, now called Adelaide Street.  Nearly seven thousand temperatures readings (Dade, 1841) were taken every day of the week by Dade at 8 am, noon, and at 5 pm.  Reverend Dade also took rainfall and precipitation measurements as well as days with rain, snow and thunder.  After he married in 1838, the couple traveled to England.  Six months later, on returning in 1839, they moved to a farm on Lakeshore Road, just to the east of the Town of Oakville.  He continued to take over a thousand temperatures and other readings for another year and a half but he only took readings twice a day.  Sometime afterward they moved to Georgetown, Ontario where Dade spent the rest of his life.

Currier print of UCC in 1835

Fig. 1   A lithograph by N. Currier of Thomas Young’s 1835 painting of Upper Canada College, looking northwest across Russell Square.


The Observer

Rev Charles Dade was born on June 20th, 1802 in Yarmouth, England.  When he was only eighteen his father died but Dade completed his masters degree from Cambridge in classics and mathematics.  After university he was admitted to the holy orders in the Church of England.  Dade was appointed Mathematics master when Upper Canada College opened.  In 1829 the college was temporarily located in the block bounded by Church, Adelaide and Jarvis Streets before moving to Russell Square in 1830.  In late 1829 Dade arrived in Canada.  Besides mathematics he also taught his students surveying techniques.  He married the daughter of the vice principal of Upper Canada College in 1838, they travelled to England, and moved to Oakville in 1839 for a couple of years.  They had two sons and a daughter.  While he never took any official position within the church, he presided over services when needed throughout his life in Canada.  He died on May 2nd, 1872 in Georgetown.


Locations and Observations by Dade and others

UCC was located 0.9 km from the lakeshore as it existed at that time.  Of the 6941 temperature readings taken at UCC in Toronto: 39.4% were taken at 8 am, 29.4% at noon, 21.2% at 5 pm, and 18.9% were missed.  The noon temperature was taken at 12:00 mean solar time and generally would have been close to the maximum temperature for the day.  The 8 am temperatures were 4.4 C colder on the average than the noon temperatures which is reasonable (NB: the units used were not mentioned in his register but were assumed to be Fahrenheit which have been converted to Celsius for this report)  Examining clear days when the noon minus morning (8 am) temperatures were ten degrees or higher, the 5 pm temperatures always exceeded the noon temperatures.  This would indicate that the location of the thermometer, if fixed, was exposed to direct and reflected solar radiation in the summer afternoons.  This leads to the assumption that the thermometer was located on the north side of a building (typical of the period) and not shaded from the northwest.  When Dade moved to a farm east of Oakville he continued to take temperatures but only at 8 am and noon.  His farm would have been about 25 km to the south-west from UCC and 0.4 km from Lake Ontario.

UCC in 1842 near King St.

Fig. 2   Upper Canada College north of King Street (Cane, 1842).


Each temperature reading was recorded to the nearest whole degree Fahrenheit.  Dade applied a diurnal correction to each monthly temperature sum which resulted in an average daily temperature for each time group.  Thus he could use all the temperatures no matter what was missing since they were now daily average temperatures.  Hence the average monthly temperature was determined from all of the readings, after the correction.  While again Dade did not detail his procedure the written calculations seem to indicate that this method was used.

Generally the 1830s monthly temperatures (Table 1) seem to follow a recent thirty year average for Toronto except that they are over two degree Celsius cooler.  The December 1831 temperature was rather cold and the following month was overly warm.  March to July temperatures closely follow the present trend.  But winter temperatures are cooler particularly February.  This could be expected from an unprotected thermometer as compared to temperatures measured in a Stevenson screen as has been standard practice for decades.  The present Toronto City temperatures are about two degrees Celsius warmer due to the heat island effect (Crowe, 1989) and the general temperature has increased with time.devine-table1

Dave's temps compared to recent averages

Table 1   Dade’s Monthly Average Temperatures in Celsius in Toronto with a comparison to the 1971-2000 Thirty Year Average.


A yearly temperature trend (Figure 3) published by Scobie in 1846 indicated that Dade’s 1830s temperature trend is close (0.1 C warmer) to that from the early 1840s taken in a fully louvred screen at the Toronto Magnetic and Meteorological Observatory which was 1.4 km to the north.  Crowe’s extended Toronto temperature trend for 1831-1837 had the same average as Dade’s.  Also the highest temperature recorded at UCC in this eight year period was 35.6 C in July 1833 and the lowest was -28.9 C on two occasions — 1832 and 1836.  The extremes for Toronto Bloor Street for the period after 1840 were +40.6 C in 1936 and -32.8 C in 1859 which bracket Dade’s extreme temperatures.  Dade’s data was for a much shorter time period and there may have been some effect due to being closer to the lake.  It should be noted that, due to infilling, the Toronto harbour front is now apx. 1/2 km further from Dade’s location at UCC.

Temperature trends in 1830s and 1840s

Fig. 3   Trend of Toronto Yearly Temperatures from Reverend Dade’s Temperatures and later from Toronto Magnetic Observatory (Scobie, 1846).


Unprotected vs. Screened Observations

There were two major concerns with temperature readings prior to the mid nineteenth century: exposure and thermometer drift.  Typically thermometers were placed on the north side of a building without much other protection.  Even the observatory at Kew in London placed their thermometer outside a north window until 1849 with no protection (Middleton, 1966).  In March 1841 the Greenwich observatory started using a ventilated screen open on the north side which had been designed by the astronomer royal, Sir George Airy.  For some reason it is called the Glaisher screen.  Thermometers exposed to the north are affected by diffuse and reflected radiation during the daytime and thermal heat loss at night.  Until 1925 the French meteorological service used a screen which was open to the north like Airy’s and in recent comparisons led to daytime temperatures as much as 3.5 C higher than a fully louvred and ventilated air temperature (Leroy & Lefebvre, 2000).  While fully louvred screens date from September 1840 in Toronto (Devine, 2007), their widespread introduction started with the acceptance of Thomas Stevenson’s small double louvred screen after modifications by the Royal Meteorological Society in 1884.  Examples of both Glaisher’s and the now ubiquitous Stevenson screens as used in 1890 may be seen in the first image here (viewed 2016/09/25).

Prior to 1800 it was noted that the ice point of mercury thermometers rose gradually (Figure 4) with time but it took over a half a century to define the problem and longer to find a solution (Middleton, 1966).  The problem was the contraction of the glass which was mostly solved by using unleaded glass, annealing the glass reeds, and allowing the completed thermometers to stand for weeks before scaling and calibration.  The ice point of spirit thermometers in contrast fell due to polymerization of the alcohol which was caused by prolonged exposure to strong light.  The ice point of two spirit thermometers of the early nineteenth century which were over a half century old, had each dropped about 1.5 C.  While the type of thermometer used by Dade is not documented, his dedication to the readings would support his using a good quality thermometer of that period.

Ice-point drift in Joule's thermometer

Fig. 4   Drift in Ice-point of James Joule’s Thermometer (Joule, 1873).



These are not Toronto’s earliest temperatures since a series of thrice daily measurements were made in York for eleven months in 1801.  Neither the observer nor the exact location within the town are known.  The measurements were published in the Upper Canada Gazette on a monthly basis (Crowe, 1989).  These 1801 temperatures appeared to have been taken in a protected area of the town possibly close to the lake where the town was located but were not taken at Fort York.  The winter temperatures readings appear to be overly warm and the summers readings overly cool.  These 1801 temperatures were the earliest temperature readings for Ontario.

What can be said of Dade’s 1830s temperature measurements?  In general the temperatures appear to be reasonable considering the period and the exposure.  The 5 pm summer temperatures are a little too high.  Care should be taken when using temperature series which predate the introduction of national networks.  Exact location, exposure and instrumentation should all be determined if possible.



“Dade’s Register of York and Oakville Temperatures, 1831 to 1840” (1831).  This is held in the historical climate archive of Environment Canada at Downsview, Ontario.

James Cane, Map of Toronto, 1842.  Also in Derek Hayes, Historical Atlas of Toronto, D&M Publishers, Vancouver, 2009.

Scobie’s Canadian Almanac, January, 1846.

James Prescott Joule, Proc. Manchester Lit. and Phil. Soc., (1873) 12, p.73, as well as “Zero Point Shift in Joule’s Thermometers”, J. Sci. Inst, 1930.

F. St. George Spendlove, The Face of Early Canada, Ryerson Press, Toronto, 1958.

W.E. Knowles Middleton, A History of the Thermometer, John Hopkins Press, Baltimore, 1966.

R.B. Crowe, Extension of Toronto Temperature Time-Series, Report No.89-11, Canadian Climate Centre, Downsview, 1989.

Michel Leroy et Guy Lefebvre, “Caracterisation de l’abri du XIXE Siecle”, La Meteorologie, 8E serie, Nu.31, septembre 2000.

Kenneth A. Devine, “The First Fully Louvred Thermometer Screen”, CMOS Bulletin, (April 2006) 34, No.2, pp.43-44.