Harrow is a weather station located 191 m above sea level, 1 km from Harrow. Its records go back to 1918: 100 years of temperature are available up to 2020, along with rainfall and a comparison with two reference normals. Closed series: the records of this station end in 2020. Over 1991–2020 the annual mean temperature there is 9.8 °C, clearly higher than over 1961–1990 (9.1 °C): a difference of 0.7 °C. The warmest year of the series is 1998 (11.8 °C) and the coldest 1924 (7.6 °C). The last complete year, 2020, ranks 12 out of 100, from warmest to coldest. Over 1961–2020, the annual mean temperature changes by +0.20 °C per decade. The station ranks 173 out of 240 stations, from the fastest rise to the slowest.
Annual mean temperature since 1918
The first ten years of the series (1918–1927) average 8.6 °C; the last ten (2009–2020) average 9.8 °C, a difference of +1.2 °C. Of the ten warmest years in the series, 2 fall after 1999. The warmest is 1998 (11.8 °C). The ten-year running mean peaks at 10.0 °C (2006) and bottoms out at 8.5 °C (1929).
Annual rainfall since 1918
On average 902 mm of rain falls per year over the 57 documented years. The wettest year, 1977, received 1328 mm; the driest, 1934, only 579 mm, which is 2.3 times less. Over 1961–1990, June is on average the wettest month (94 mm) and February the driest (51 mm). Between 1967 and 1993, 12 years out of 20 exceeded the series average.
Monthly normals: 1961–1990 against 1991–2020
The table compares, month by month, the mean temperature and the rainfall total of two thirty-year reference periods. The difference column shows what the recent period changes compared with the earlier one.
| Month | Temp. 1961–1990 | Temp. 1991–2020 | Difference | Rain 1961–1990 | Rain 1991–2020 | Difference |
|---|---|---|---|---|---|---|
| January | −5.0 °C | −3.7 °C | +1.3 °C | 55 mm | – | – |
| February | −4.0 °C | −2.5 °C | +1.5 °C | 51 mm | – | – |
| March | 1.6 °C | 2.2 °C | +0.6 °C | 72 mm | – | – |
| April | 7.9 °C | 8.3 °C | +0.4 °C | 84 mm | – | – |
| May | 14.3 °C | 14.8 °C | +0.5 °C | 88 mm | – | – |
| June | 19.6 °C | 20.4 °C | +0.8 °C | 94 mm | – | – |
| July | 22.1 °C | 22.6 °C | +0.5 °C | 83 mm | – | – |
| August | 21.1 °C | 21.6 °C | +0.5 °C | 93 mm | – | – |
| September | 17.4 °C | 17.8 °C | +0.4 °C | 90 mm | – | – |
| October | 11.0 °C | 11.5 °C | +0.5 °C | 63 mm | – | – |
| November | 4.8 °C | 5.0 °C | +0.2 °C | 87 mm | – | – |
| December | −1.8 °C | −0.5 °C | +1.3 °C | 94 mm | – | – |
The largest temperature change is in February (+1.5 °C) and the smallest in November (+0.2 °C); over the year the mean difference is +0.7 °C, and 12 months out of twelve are warmer than before.
Records at Harrow
- Warmest year: 11.8 °C, in 1998
- Coldest year: 7.6 °C, in 1924
- Driest year: 579 mm, in 1934
- Wettest year: 1328 mm, in 1977
- Warmest month: 25.1 °C, in July 1999
- Coldest month: −11.1 °C, in January 1918
- Wettest month: 323 mm, in May 1892
4.2 °C separate the warmest year of the series from the coldest. Daily records are not part of the dataset for this station: only annual and monthly extremes are shown.
Temperature trend over 1961–2020
The regression line of annual mean temperature changes by +0.20 °C per decade between 1961 and 2020, about +1.2 °C over the whole period. That is slower than the median of the 240 stations (+0.25 °C per decade), by 0.05 °C per decade: the station ranks 173 out of 240.
Data source and licence
Data source: Environment and Climate Change Canada (dataset “AHCCD (ahccd-monthly) + climate-daily”), licence Open Government Licence – Canada. Last updated: 29 October 2026.
The data for Harrow are shown as the source publishes them; this site does not correct them. A year is kept only if at least eleven months of measurements are available, and a normal is computed only with at least twenty years of data out of its thirty. Temperatures are rounded to 0.1 °C and rainfall to the millimetre. The station is one of 240 stations in Canada: the overview page lets you compare them.
Frequently asked questions
What is the annual mean temperature at Harrow?
Over 1991–2020, the annual mean temperature at Harrow is 9.8 °C. It was 9.1 °C over 1961–1990, a difference of +0.7 °C.
What is the warmest year ever measured at Harrow?
Since records began in 1918, the warmest year at Harrow is 1998, at 11.8 °C on average. The coldest is 1924 (7.6 °C).
Is the climate at Harrow getting warmer?
Yes: at Harrow, the annual mean temperature rises by 0.20 °C per decade between 1961 and 2020, +1.2 °C in total. 2 of the 10 warmest years in the series fall after 1999.
Towns near this station
Neighbouring stations