Very warm first half of January for Sydney, up and down in Jyväskylä

The 2015 edition of January has seen a rather warm first half at Sydney Airport. Of the first 15 days, 13 of those surpassed 25C. The same number also remained above 20C.

Minimums have been especially warm, as illustrated in the first graph below. While the actual daily figures themselves haven't been anywhere near record levels (2009, 2011 and 2013 recorded higher minimums than this month's highest of 23.2C so far), the consistent run above 20C has helped the average so far stay above 21C.

Bureau of Meteorology methods for recording daily temperatures differ from mine, but their current figure of 21.3C is still well above the highest overall since 1940. For the record, my measurements give an average of 21.4C so far. According to Bureau records, the highest average minimum for a January at the Airport is 20.8C, from both 1991 and 2011. Current forecasts support the idea of this January breaking the record.

Progressive average minimum for January at Sydney Airport for the period 2009-2015 plus the long term average

While all Januaries in the years between 2009 and 2014 saw the average maximum sit below 28C at some point, this January has yet to see that happen. So far seven of the 15 maximums for the month have surpassed 30C. By the same point in the other six years, none had seen that many. 2013 was the next closest with six, while 2012 had only seen one.

Forecasts show the average holding above 28C, but they're likely to be below the figure from 2013 by the 18th. If some hotter days appear towards the end of the month, 2015 could climb to the top of the pile. 1991 also holds the record here with an average of 29.2C.

Progressive average maximum for January at Sydney Airport for the period 2009-2015 plus the long term average

Recent fluctuating temperatures in Jyväskylä, which have included six of the 15 maximums so far above 0C, but also four at or below -10C, have led to a fairly average start for January. The overall average at this point actually sits a little warmer than the 1981-2010 figure; -7.6C compared to -8.3C.

The average minimum has seen movement above and below the -10C mark in the recent week, but it is still holding below the respective figures from 2012, 2013 and 2014. Other than the cold January of 2010, average minimums from the other years since 2009 ended up within a couple of degrees of each other.

Forecasts for the next 10 days will put 2015's line somewhere just below that of 2012. It'll come down to the final week of January before we can see the final average and where it is placed among the recent six years.

Progressive average minimum for January at Jyväskylä Airport for the period 2009-2015

Warm maximums opened January's account this year, but temperatures quickly dropped after a few days. Based on predictions, we could see 2015 as the highest progressive average by January 17. Decreasing temperatures again next week though will force the average back down. If current forecasts for maximums at -15C and below for the end of next week come true, 2015 will place itself somewhere in the middle of the years excluding 2010.

Progressive average maximum for January at Jyväskylä Airport for the period 2009-2015