Storm at Dusk
This summer had 7 very hot days above 40°, and 11 very hot nights above 24°.
The worst heat waves came in January. Around the 17th, weekly temperatures were more than 6° above normal, with days at about 41°, and nights 24°. Near the 28th, nights were even warmer. Episodes of very low dew point came at times of lower temperature.
Thirteen rain days were scattered through the season, the highest readings being 25.0 mm on 16 December and 18.0 mm on 21 January.
Comparing summer seasons
Average temperatures were almost the same as in the hot summer of 2016-17. Days, at 35.5°, were slightly cooler and nights, at 20.1°, slightly warmer. The resulting average, 27.8°, was a new record summer temperature, beating 2016-17 by 0.2°.
Remarkably, the mean subsoil temperature, 25.5°, was not high, but normal.
Similarly, daily temperature range (15.4°) and cloudiness (22%) were normal. (Recent summers have been cloudy.) Dryness was shown only by very low humidity and rainfall.
The mean early morning dew point for this summer (10.4°) was second lowest in the 19-year record. Only that of summer 2013-14 (8.6°) was lower.
The total rainfall for the summer, 70 mm, was equal second driest with 1965, the driest summer being 1930, which had 66 mm.
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. Station 55312 recorded no readings this summer. I used my own readings for the whole season.
All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.
The first heat wave of the month was nearly five degrees above normal: a little worse than last January’s. Rain, mainly on the 12th, brought a cool spell with very dry air. A second heat wave was not so bad, and it was gone by the 31st.
Three days went over 40° (but January 2003 had five) and three nights did not go below 25° (a January record).
Rain fell on five days (usually seven), the highest reading being 15 mm.
Comparing January months
The average temperature this January (27.9°) was not as high as last January (28.7°), or even January 2013 (28.2°). The days (36.2°) were second hottest after 2017 (36.4°), but the nights (19.7°) were only fourth hottest.
The estimated rainfall of 20.6 mm was low: at the 11th percentile, and only one quarter of the January average (87 mm). However, there are still no serious rainfall shortages. The lowest percentile value (12th percentile) is the five-year total of 2760 mm, which is 440 mm below the normal five-year total of 3200 mm.
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, but it is not. The gauge last reported on 24 September 2017.
All data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.
This summer, like summer 2013-14, was marked by repeated heat waves. The first, early in December, was brief. Another, in mid-January, led into one that was hotter, and persisted through the first half of February. On a weekly basis, temperatures did not fall below normal at any time in the season. Mid-February had the two hottest days of the new century, at 44.9° and 43.8°.
Although there were as many rain days as usual (22), only two days had rainfall exceeding 15 mm, and there was almost no rain in February.
Comparing summer seasons
Mean temperatures set new records for the summer season: daily maximum 35.6°, average 27.6°, and daily minimum 19.7°. Each of these was more than a degree higher than the old record. Nearly all such figures for the months December, January, and February had also been records. However, the subsoil temperature for the summer (24.7°) was low.
Two indicators of moisture were a little low: mean early morning dew point (13.4°) was down 0.7°, and mean daily temperature range (15.9°) was 0.8° wider than usual.
The percentage of cloudy mornings (38%) was almost the same as in the last four summers, and lower than in the previous two. However, 38% is much more cloudy than the “normal” figure of 31% cloudy mornings that was set in the decade 1999-2008. Summers were more sunny then.
This summer’s rainfall was very low. The unofficial total of 101.4 mm would place it as the seventh driest on record. As shown on the graph, summer 2013-14 was drier (85 mm). Otherwise, there has not been a drier summer in the half-century since 1964-65 (70 mm).
[The following summer (Summer 2017-18) was not as hot and had more rain.]
Data. Rainfall figures are usually from the automatic rain gauge at Manilla, published on the internet by the Bureau of Meteorology as Station 55031. However, the gauge ceased recording five months ago (8/10/16), and this month’s readings are from my non-standard gauge. All data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.