Frances commented on the evening of 31 May that "Tomorrow is the first day of Winter." so it behooves me to comment on the summary of the last three months representing Autumn (or as those from the Evil Empire across the Pacific call it, "Fall").
Autumnal Review
My Weather station has now recorded data from Angophora Drive for 7 Autumns. These are summarised in the page 'Seasonal Summaries' in this Google Sheet. Summarising further:
- The average daily minimum temperature was the warmest, by 0.3C, of the 7 seasons. It was 1.01C above the average of the 6 earlier years.
- The average daily maximum temperature was the warmest, by 0.9C, of the 7 seasons. It was 1.31C above the average of the 6 earlier years.
- (In both cases the 'runner up' was 2019.)
- Although the station is not well exposed to wind it is interesting that the wind run for the three months is the second lowest of the 7 years. (This may reflect growth of garden shrubs rather change in the weather!)
- Rainfall was the second highest (90 mm below 2022) and still 150mm above the average.
Monthly material
The month was very wet (only 3 of 46 previous Mays recorded more rain) and warm (temperature anomaly of +1.14C. Relative humidity was at the high end of the 7 years for which I have data (but not extreme - whether examined for the standard times or for the average of the month as a whole. Wind run was very low: possibly reflecting a higher than usual proportion of BoM wind records from the Eastern half of the compass, from which my WS is fairly sheltered.
Rainfall
In a post on 23 May to the Facebook Group I commented:
"I was a little surprised yesterday morning at how little rain was being recorded on my WS compared to what I was seeing. On going to check the WS I found that the rainfall collector was full and the filter was blocked by green slime. Never had that happen before in the 12 years I have had the device. Removing the filter let the liquid run through, tipping the cup 10 times!Comparing the WS records with my Nylex suggests it has been missing about half the falls in the last few weeks. (I am quite happy with records to the end of April.) A comparison with BoM records for the Airport and Gabo, and information from Marty suggests that doubling my records for 18-19 May will give a fair estimate of reality so I have done that. Recording immediately started to match what I was seeing."
So it is possible my records for the month as a whole are a little understated. I totalled 156.6mm for the month, amounting to 214% of the median for May. For the year to end May we are at 633mm which is 176% of median falls to the end of May. Here is a chart of daily fall, including the adjustments described above (note that there are several days early in the month with a record of 0.2mm which barely show up in the chart):
I have added a section at the end of this report comparing 2025 rainfall at the BoM Airport and Gabo Island sites.
Temperatures
The development of the anomaly (difference to long-term mean) shows a cool first few days followed by a warm spell, sustained to the end of the month.
A chart of daily extremes give a pattern consistent with the above.
Minimum temperatures
The average minimum for the month was 10.05C, 0.73C above the average minimum for May recorded on my WS. The lowest I recorded in the month was 5.3C on the 20th: one of only 3 days significantly below the long term average minimum for May. The highest minimum temperature was 14.9C on the 23rd: 4 days were significantly above long term. Overall 22 minima were above average and 9 below.
Comparing with recent years the time series for average monthly minima over financial years shows a continuation of 2024-25 as being warmer that usual.
Maximum temperatures
The average maximum for the month was 19.67C, 1.54C above the average minimum for May recorded on my WS. The highest I recorded in the month was 27.0C on the 6th: one of 10 days significantly above the long term average maximum for May. 3 days (5th to the 7th) were very significantly above average. The lowest maximum temperature was 11.7C on the 18th: 2 days were significantly below long term. Overall 23 maxima were above average and 8 below.
Comparing with recent years the time series for average monthly maxima over financial years shows a continuation of 2024-25 as being warmer that usual.
Humidity
The records for the month were reasonably normal for such a rainy period.
Wind
See comment in preamble.
Extra: Rain at Airport and Gabo
This section arose from a feeling that rainfall recordings at Gabo were lower than I expected compared to those at the Airport. For the year to date the 2025 ( to 28 May) falls recorded by BoM at the Airport and Gabo were 682mm and 478 mm respectively. Comparing the daily falls over 148 days there were:
- 78 days where both sites reported the same amount (mainly 0mm!)
- On another 54 days the difference was less than 5 mm one way or the other.
- On 13 days the Airport recorded greater than 5mm more than Gabo; and
- On 3 days Gabo was more than 5mm above the Airport.
Three days stand out where the Airport recorded much more than Gabo which I think gave rise to my feelings of doubt:
- 8 February 42.4 mm vs 4.2mm
- 10 February 73.4 mm vs 10.8 mm
- 24 May 76.2 mm vs 49.4 mm
However I think that looking at the overall series I could not conclude there was any consistent pattern I could raise with BoM.
I did also look at Green Cape (GC) but found that 14 days had missing readings and for another 5 days the falls were cumulated over more than 1 day. One of the missing data periods, in January, included a significant rain event (27 mm at the Airport, 14 at Gabo). I also couldn't pick a consistent pattern between GC and either of the others where data was available for all three sites.
My conclusion was that while the differences were surprising given the 2 sites are quite close (17km in a straight line) with apparently similar exposure and neither site affected by hills (on 8 -10 February the wind at Gabo was from SE, on 24/5 it was from NW but Howe Hill is ~8km away), explaining this was above my pay grade!
