Temperatures did not stray far from normal. The first (black) frost that I observed was on the 15th, near the normal date for it (13th May). That began a week of sunny skies and very dry air.
There was only one rain day. An early morning shower gave a reading of 1.2 mm on the 30th.
Comparing May months
The May months in 2018, 2017, and 2016, as well as in 2014, were all warm. The average temperature was more than half a degree above the normal value of 13.3°. While May 2017 was warm, wet, and humid, May 2018 was warm, dry, and arid. The air was exceptionally dry, with the mean early morning dew point (0.0°) the lowest for May, and the relative humidity at that time 68% instead of the usual 80% to 90%.
The rainfall total of 1.2 mm was third driest for May, equal with May 2002, but not as dry as May 2006 ( 0.2 mm). Only May 1927 was drier, with zero. May rainfall values have been low in the 21st century, with an average of 23 mm, compared to the long-term average of 41 mm.
Last month, April 2018, had only two rainfall shortages classed as “serious” (below the 10th percentile): those for durations of five years and six years. Since then, more shortages have appeared. Those five-year and six-year shortages remain, but there are now serious shortages for durations of five months and twelve months, and severe shortages (below the 5th percentile) for one month, two months and three months. The current three-month total (45 mm) is at the 4th percentile.
Data. A Bureau of Meteorology automatic rain gauge operates in the museum yard. From 17 March 2017, 9 am daily readings are published as Manilla Museum, Station 55312. These reports use that rainfall data when it is available. The gauge, which had last reported on 24 September 2017, came on line again on the 16th of March. However, during the month of May eleven daily readings were blank. I have substituted my own gauge readings, which were all zero.
All data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.