Contents

• Temperatures
• Average Temperature
• Record Temperature
• Monthly Temperature


• Link
• Climate Change

• Precipitation
• Average Precipitation
• Record Precipitation
• Monthly Precipitation
• Seasonal Precipitation
• Precipitation Variability
• Is it a Drought?

• Year in review
• This Year
• Last Year
• Long-term Trends
• Gardening

Average Temperature

Average monthly maximum and minimum (°C) from 1992 to 2010.

Record Temperature

Record monthly maximum and minimum (°C) from 1992 to 2010.

Monthly Temperature

Maximum and minimum (°C) for the most recent month, from 1992 to 2010.

Average Precipitation

Average precipitation (mm) by month from 1992 to 2010.

Record Precipitation

Record precipitation (mm) by month from 1992 to 2010.

Monthly Precipitation

Precipitation (mm) for the most recent month, from 1992 to 2010.

Seasonal Precipitation

Precipitation (mm) by season, from 1992 to 2010.

Precipitation Variability

Anecdotal accounts claim that precipitation in June is more reliable than in other spring months. Is this true?

The evidence suggests otherwise: June appears unremarkable, neither more reliable nor more variable than other months. September, on the other hand, is quite unreliable. This makes sense, as it could either be the end of the dry season or the beginning of the wet season. December and January are not very variable: they tend to be uniformly wet.

Coefficient of Variability for precipitation.

Is it a Drought?

I have been asked if we are "officially" in a drought. The answer is that it depends what you mean by drought. There are many different standards, all of which are subjective, so it is not a term used by climatologists.

Climatologists use various mathematical indices to compare precipitation to long-term averages. One of these is the Standardized Precipitation Index (SPI). The following graph shows the SPI for Denman Island for the last 20 years. (The calculation includes data from the last 98 years, so "normal" is defined mostly by data that are not shown on this graph.)

As you can see, most of the last 20 years have been on the wet side of normal, including some extremely wet years. Starting early in 2008, the trend reversed rather abruptly, heading rapidly to the dry side of the scale. If you use the word "drought" for the "Extremely Dry" category of the index, we are not there yet.

For a while, it looked like we were heading in that direction. More recently, the trend seems to have levelled out. In late 2009, it returned to more normal levels. It is too early to make any predictions.

Standardized Precipitation Index

This Year in Review

Temperatures for 2010.

Precipitation for 2010.

Last Year in Review

Temperatures for 2009.

Precipitation for 2009.

Long-term Trends

Average Precipitation 1907-2007

The difference between the 1906-1992 data and the 1993-2007 data may be due to climate change or due to the measurements being taken at a different recording station.

Total Precipitation 1911-2009

Gardening

Since the 1960s, the frost-free period has increased significantly. The change has occurred at both spring and fall. The chart above shows Denman information, but the data from Comox airport confirms that this is a real trend.

According to Agriculture Canada's map, Denman Island has has apparently been overlooked when it comes to its horticultural zone classification. The closest classified areas are Buckley Bay (zone 7b), Comox (zone 7a) or, if you really want to brag to your friends on the Prairies, Texada Island (zone 8a). Take your pick.