A November day hotter than any one in October

The high temperature on the 8th got up to 18 degrees which was hotter than any day we saw in October and was the warmest day since September 27th.

Also as pointed out in the comments on the October summary by Rob Kuhn: the temperature didn't go above 20 degrees in all of October, which hasn't happened since 1987.

And in fact the 17.2 degree extreme high temperature this October was almost the record lowest since records began in the area over 90 years ago. We ended up tying 1925 when 17.2 was also the warmest temperature seen in October, but in every other year there was at least a single day that was warmer. My apologies for not recognizing this and putting it in the summary.

October 2009 Summary

October was wet with cold days and warm nights

Just looking at the overall average temperature for the month it was about half a degree below average, this is still within the average range so it was officially an average month for temperature.

However, digging a bit deeper into the numbers, it was another month where there was a large difference between the daily high and low temperatures. The daily high temperatures were 1.5 degrees below average while the daily low temperatures were actually 0.4 degrees above average. As I have pointed out in the past, I’m of the belief that most people are more aware of the high temperature of the day and thus would have perceived October as a very cold month.

Looking at the graph of the temperature, you can really see the week between the 11th and the 17th where it was more than 5 degrees below average and how the temperature rebounded in the last half of the month. The first frost of the year happened on the evening of the 11th, a little later than the average date which is the first of the month.

During the first 10 or so days of the month it looked like we might be on track for a record wet October, but then almost 2 weeks of dry weather put in an end to that. A few storms in the last week put the total precipitation for the month at 84.4 mm, more than enough greater than the average of 67.1 mm to classify it as above average.

With the total precipitation for the year (784.7 mm) still close to the average (748.3 mm), it will take some pretty extraordinary numbers in these last couple of months of the year to get us out of the average range.


Summary for October 2009:
Maximum Temperature 17.2 °C
Minimum Temperature -4.7 °C
Average Daily High Temperature 11.7 °C (Long term average 13.2 °C)
Average Daily Low Temperature 3.2 °C (Long term average 2.9 °C)
Total Precipitation 84.4 mm (Long term average 67.1 mm)

(Long term averages based on 1971-2000 data for the Waterloo Wellington Airport)

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Coldest daytime high in 6 months

The high temperature on the 15th was only 3.4°C, that was the coldest high temperature since April 7th when it was -1.5°C.

No doubt about that one

Sometimes the first frost day just kind of skirts below zero for a few 15 minute readings. But this time with the temperature below zero for a good 11 hours starting on the night of the 11th there is little doubt that our frost free season is over.

Historically the first frost day in the area usually happens around October 1st, so we are a bit later than average. Looking at the forecast it looks like there are going to be some more cold night coming up.

September 2009 Summary

A hot and dry September

This was a month with two distinctly different parts; the first two thirds had slightly above average temperatures and a lot of sun (on the temperature graph you can see the large diurnal swing indicative of clear skies). During the last third of September the clouds came and the temperature generally went off a cliff (on the graph there is a lot more consistency in the daytime and nightime temperatures). Overall it was about a degree above average which is the highest for any month of this year.

Up until the last week of September it looked like it might have been an historically dry month, as there was no significant precipitation for the first 20 days. But then the wettest day of year came along (30.2 mm on the 28th) and although the total was still below average, it was no longer historically low.

This dry month brought the total precipitation for the year (700.3 mm) very close to the average (683.5 mm).


Summary for September 2009:
Maximum Temperature 24.7 °C
Minimum Temperature 1.9 °C
Average Daily High Temperature 21.0 °C (Long term average 20.0 °C)
Average Daily Low Temperature 9.6 °C (Long term average 8.3 °C)
Total Precipitation 51.4 mm (Long term average 87.5 mm)

(Long term averages based on 1971-2000 data for the Waterloo Wellington Airport)

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