Warm start to December in both cities

Both Sydney and Jyväskylä have seen an above average start to December. Warm and sticky weather punctuated by storms has been seen in Sydney, while temperatures in Jyväskylä haven't been anywhere near the lows typically experienced at this time of the year.

Three of the four progressive averages as seen below are the highest among the past few years. The average minimum for Sydney is the second highest.

Progressive average minimum for December at Sydney Airport for the period 2009-2014 plus the long term average

The average minimum for Sydney had continually been above 19C until yesterday, the 14th day of the month. Yesterday saw the coldest temperature so far this month, a minimum of 15.6C. Since 2009, 2010 was the only other year not to see a temperature below 15C in the first half of December.

Currently forecasted minimums for the coming week put 2014's line above that of 2010. The forecasts for recent days, however, have been slightly off. For example, the prediction for yesterday was for a low around 18C, yet it dropped more than 2C below that.

Progressive average maximum for December at Sydney Airport for the period 2009-2014 plus the long term average

Other than 2011, which holds the record for the lowest average maximum with 22.6C, other years saw fairly similar progress after the first two weeks and a similar final figure above the long term average. December this year saw the first eight days of the month surpass 28C at the Airport and the average held above 30C for a week long period after the 2nd. Temperatures have been a little cooler since the middle of last week though. The highest temperature between the 11th and 13th was only 23.5C.

Based on current forecasts, the average maximum will remain above the previous five years until December 20 when it dips below 2013's figure. There'll have to be plenty of hot days towards the end of this December for it to achieve record levels though. 2005's 29.5C is a fair way off the projected 27.3C by the 22nd.

Progressive average minimum for December at Jyväskylä Airport for the period 2008-2014

After two minimums below -5C to the start the month, the only two such recordings so far, the average minimum at Jyväskylä Airport has climbed to the top of respective figures after the first half of December. The lack of cold temperatures is clear. All of the remaining 15 days so far have failed to go below -3C. 2008 and 2011 saw the next nearest number with 9 days above -3C. 2010 and 2012 saw no minimums higher than -3C for the same period.

Cold temperatures may finally be on the way though. Forecasts have again been fluctuating quite a lot for the coming 10 days, but temperatures could drop to -15C or lower next Monday or Tuesday. If this forecast is correct the average minimum will drop below the figures from 2008 and 2011.

Progressive average maximum for December at Jyväskylä Airport for the period 2008-2014

For the average maximum, the orange line sits above the others once again. December 2014's warm start has seen only two days that remained below zero. And even then the coldest so far was December 1's -0.6C. For some comparison, in the first 15 days of December in 2009, 2010 and 2012 the coldest respective maximums were -17.8C, -18.9C and -18.8C.

The next few days should remain fairly mild with temperatures hovering around 0C or just below. A high of -8C is currently predicted for December 23 and that would help the average drop below that of 2011 and 2013. As I said though, the forecasts have been changing rather quickly in the past couple of days and there is a lot of uncertainty over temperatures following the end of this week. For example, yesterday the predicted maximum for December 23 sat at 3C.