with John Maunder
The average afternoon temperature in Tauranga in May 2018 was 18.1 degrees C.
In contrast, May 2016 was equal with May 1916 as the warmest May on record, both recording 19.3 degrees.
Temperatures have been recorded in the Tauranga area at several sites during the last 100 years, including the current Tauranga Airport site from June 1990.
It's very common for areas, such as Tauranga, to have experienced different observation sites during the years – and the readings from the earlier sites have been adjusted to the present site using standard climatological procedures.
It's considered the temperature series described here is a fair and true record of what the temperature would have been if the current observation site (of Tauranga Airport) had been used throughout the period.
Traditionally, temperature observations have been recorded with a set of maximum and minimum temperature thermometers.
These record the daily maximum temperature – usually recorded in mid-afternoon – and daily minimum temperature – usually recorded just before dawn.
This analysis of temperatures for Tauranga is for the average daily maximum temperatures.
The graph shows details of the average daily maximum temperatures, called simply ‘afternoon', for Tauranga for May from 1913-2017. May 1964 is not included because of incomplete data.
The long-term average afternoon temperature in May for Tauranga is 16.9 degrees Celsius, ranging from the cool May months of 1936, 1940, and 1997 with an average afternoon temperature of 14.9 degrees Celsius, to the warm May months of 1916 and 2016 both with an average afternoon temperature of 19.3 degrees Celsius, May 2011 with 19.1 degrees Celsius, and May 2007 with 18.9 degrees Celsius.
The graph of the average afternoon temperatures for May shows generally normal variations from May to May.
However, the last 20 May months have been a little warmer than other May months since 1913.
From 1913 to 2018, there have been 14 May months with an average afternoon temperature of 18 degrees Celsius or more, and 11 May months with an average afternoon temperature of less than 16 degrees Celsius.
The value for May 2013 was 18.5 degrees Celsius, which is the sixth warmest on record, and for May 2014 the temperature was 18.4 degrees Celsius – the seventh warmest on record, and May 2016 which was equal first warmest on record.
The 14 warmest May months, in terms of afternoon temperatures, on record in chronological order are: 1916, 1928, 1938, 1950, 1999, 2000, 2003, 2005, 2007, 2010, 2011, 2013, 2014, and 2016.
In contrast, the 11 coolest May months, in terms of afternoon temperatures, on record in chronological order are: 1913, 1920, 1924, 1936, 1940, 1945, 1959, 1967, 1977, 1983, and 1992.
The average afternoon temperature in May during the 49-year period 1914-1962 was 16.7 degrees Celsius, compared with 17.1 degrees Celsius for the 49-year period from 1963-2011.
For further information see https://sites.google.com/site/climatediceandthebutterfly/