Weather Eye with John Maunder

Rainfalls for the month of May have been recorded in Tauranga since 1898 – except for 1904, 1907, 1908, and 1909 – and the city's fifth driest May occurred last month.

The graph shows the range of rainfalls from an extreme high of 634mm in 2005 to a low of 13mm in 2001. The rainfall for May 2014 is 28mm – the fifth driest May since records became available in 1898.

The second wettest May was 1950, when 311mm was recorded, and the second driest May was in 1918, when only 24mm fell. The long-term average rainfall for Tauranga for May is 124mm.

Apart from the exceptional rainfall of 634mm in May 2005, the graph shows a small decrease in overall May rainfalls when two 50-year periods are compared.

The average May rainfall of 127mm during the 50 years from 1911-1960 has dropped to 115mm during the five decades from 1961 to 2010.

Since 1898, there have been 14 May months with a rainfall of 200mm or more. In chronological order, the wettest May months are: 1899, 1900, 1917, 1925, 1926, 1928, 1949, 1950, 1956, 1961, 1962, 1971, 2005, and 2010.

In terms of dry May months, there have been only nine May months with rainfall of less than 40mm. In chronological order, the driest May months are: 1901, 1918, 1939, 1941, 1978, 1991, 1999, 2007, and 2014.

Of particular significance is the exceptional rainfall in May 2005. I estimate such a rainfall is likely to occur in Tauranga only about twice in every 1000 years.

This suggests central government could have had a much more important role in financial implications of the floods, which affected many areas of Tauranga in May 2005.

For further information about the climate of Tauranga and other climate matters, see https://sites.google.com/site/theweatherclimateeye/