September 2026 Mallacoota Weather report

 In summary, continuing the recent experience of a warm and very dry month.  

Some summaries of key data are in this Google Sheet https://docs.google.com/spreadsheets/d/1eMbGfeSMKo6Hw1HFJqmNgQ1MIXpi_HV1oZdxyYi5Ir0/edit?usp=sharing 

Rain

It would be nice to get some.  This month totalled 27.7 mm with falls above 0.2 mm on 7 days.  For comparison BoM Airport recorded 18.6 mm and BoM Gabo 21.6 mm.  The Wunderground site at Nungatta  only managed 16.8mm.

The WS fall is 41% of the median fall for the month and positions the full year to date (486 mm) at 72% of the median fall to the end of September.  The falls in February and April give a less depressing look to the YTD series.

Not surprisingly my prorata estimate of the fall to the end of the year confirms the sorry story with estimated annual total of 687 mm rating as the 3rd lowest fall since BoM Airport records began in 1975.  I suspect/hope it is unlikely we will match the lowest fall (531mm in 2019) as that would mean only 31mm total for the remaining 3 months.

As an alternate view of the situation I calculated the average cumulative rainfall to date and the equivalent for 2026.  The next chart shows the difference: I think this is reasonably clear!

Temperatures

The temperature anomaly finished the month at +1.06oC with relatively little variation through the month.

The time series of anomaly values shows a resumption of the upwards movement., particularly in the moving average (red line) which eliminates seasonal effects.

The plots of daily extremes show a lot of variation particularly for the maximum series.

It was noticeable that the range of daily temperatures was quite broad, with the range above average for the day on 19 of the 31 days. The mean daily range was 2.5oC wider than the average for September.

Minimum Temperatures

The average daily minimum temperature was 9.01oC, placing the month in the middle of recent observations for September.

THe lowest temperature recorded in the month was 4.3oC against 0200 hrs on the 28th.

As for last month I checked the timing of the minimum temperatures.  In September 12 of the minima were recorded against 2200 hrs and 1 against 1800 hrs.  Under BoM rules all of these would be counted against the following day, making it very difficult to compare the two systems.

Maximum temperatures

The average daily maximum temperature was 21.09oC, placing the month as the warmest recent observations for September.  (It is difficult to compare with the BoM site as sea breezes, to which my WS are not exposed, cool the maximum on most days.)

I also checked the timing of the maxima.  As expected nearly all of them were against 1000hrs or 1400hrs but 2 were against 0600hrs (in one case with the same temperature recorded at 1000hrs) and once at 0200 hours.  These would all be logged by BoM against the previous day.

The hottest temperature recorded this month was 31.5oC against 1000 hrs on the 20th.  This was the 2nd hottest September day recorded on my WS, with the hottest being 34.5oC on the 19th September 2023.

Humidity

The daily humidities at my standard times (to suit the hours at which Ecowitt Monthly protocol delivers) show a normal pattern albeit with 3 days with very low readings.

The lowest readings for the low days, in all cases against 1000hrs, were even lower than the standard hours.  On the 19th and 20th the lowest readings were 20% and 21% respectively and on the 30th again 21%.  Looking at the previous records for my site there are only

• 5 days with humidity readings below 20% (3 of them in Septembers);

• 4 days with an rH of 20%; and 

• 3 days with an rH of 21% 

So such values are unusual but not impossibly so.

The average morning value (74.7%) was surprisingly a little above both 2025 and the average value.

The afternoon value was well below both other values.

Wind

September is the traditional month of “gales of the equinox” but this month was somewhat calmer than might have been expected.  No day had very strong winds ….

…. and the average maximum gust was lower than 2025 and the recent average.

Solar 

Fairly even through the month with drops around the days with “rain”.

Floriferousness off Genoa Rd

 Frances has been exploring various tracks off the part of Genoa Rd just West of the built up area, so we decided to take a look at a few spots around noon on the 30th September.  It was quite warm and sunny which encouraged Sun Orchids to appear.

There were masses of Spotted Sun Orchids (Thelymitra ixioides) in the slashed area under the power lines opposite Karbeethong Rd.

I think these yellow Sun Orchids are T. flexuosa.  Sorry for the blurriness: my phone was keen on focusing on the background (and I am out of practice, so didn't think to take my cap off as a less distracting backdrop).  The next day was solid overcast and all the sun orchids were closed.

I think this is T. rubra as there is a dark band just visible on the column.  There were many of these in the area behind the information sign.

We explored the area leading in to the Water Treatment Plant (NOT Watertrust Rd).  Several Large Flying Duck Orchids (Caleana major).  I went back to the area the next day and with the aid of folder, to give a plain background got a couple of better images.

I think this was T. carnea as it was a little paler pink and no dark band.

A Purple Beard-Orchid (Calochilus robertsonii).

On the later visit I also added Caladenia catenata.

We also explored the start of Captains Creek Firetrail but the area where there used to be many Large Flying Duck Orchids and Brown Beak Orchids has been thoroughly graded so no orchids.

There were a good few other flowers under the power lines.  I didn't take a lot of snaps but here are some.  I always like Comesperma ericinum.

This next one has me (and iNaturalist) bluffed.  It didn't bluff Bryce who identified it as Boronia mulleri:  we had considered that but it had very little scent.  A distant shot ....

... and a closer one.

A Thelionema lily.

There are still some damp parches in the track beside the power lines and that seemed to be attracting lots of these moths, which iNaturalist has identified as Bogong Moths (Agrotis infusa).

August 2026 Weather report

 Continuing the recent experience of overall mild temperatures (cool minima and warm maxima)and very little rain.  

Rainfall

Total rainfall at my Weather Station (WS) was 29.2 mm.  This is 46% of the median August fall and compares with 23.8 mm at the BoM Airport site; 21.2 mm BoM Gabo Island and 32 mm at a Wunderground site at Nungatta. The first chart shows a comparison with recent monthly falls.

The sorry picture is confirmed by looking at the falls expressed as a % of the median fall for each month and for the Year To Date.

I have also compiled my usual pro-rata estimate of the annual fall.  Not surprisingly that is showing levels well below the last two years and the trend line is not looking good.

To give a longer term comparison I have compared the pro-rata estimates for this year with those for 2019 (which ended at 548mm and the fire).  Not promising, even though this year is a little higher than 2019.

Temperatures

The overall temperature anomaly for the month was 0.68o C.  As shown in the following chart the month began with a cool spell and gradually warmed.

A time series of values of the anomaly shows it having apparently reached a local turning point, shown by the moving average, and continuing a downwards trend.

A chart of the extremes shows the contrasting behaviour of the maxima and minima.  This will be discussed further in the next two sections.  

Whenever there is an interesting result I contemplate Trewin’s Hypothesis “Any interesting statistic is probably a processing error.”  In this case I compared the daily extremes with those from the BoM Airport site.

The match with minima is excellent and the higher values of maximum for the maxima is as expected from past comparisons.  So, good stuff,

Temperature ranges

I noted that in many days the temperature range shown by my WS was well above the range of the averages.  Overall, the range was on average 2.7o C wider for 2026 than the average since 2019.  

Minimum Temperatures

The lowest temperature recorded this August was 3.7o C on the 1st.  This is the 8th lowest August minimum for my WS site with the coldest being 1.9o C (an official frost!) on 24 August 2019.  

The average minimum temperature for the month was 7.08o C, lower by 0.63o C than the average minimum for August.  This places it at the low side of the series of average minima.  

8 of the month's minima were significantly below the monthly average and 3 were significantly above the monthly average. 

As an aside, I was interested to see that 12 of the minima were recorded against 2200 hrs.  Thus using the silly BoM 0900 daily reset these temperatures would be counted against the following day!

Maximum Temperatures

The highest temperature recorded this August was 21.3o C on the 3rd.  Somewhat surprisingly, as it is not significantly above the monthly average, this is the 15th highest August maximum for my WS site with the hottest being 26.8o C on 30 August 2020.  

The average maximum temperature for the month was 18.74o C, higher by 2.00o C than the average minimum for August.  This places it at the high side of the series of average maxima a little below the 19.2o C average for August 2024.

None of the maxima for the month were significantly about the average.  The most notable feature of the monthly maxima was that there was only 1 day - the 31st! - with a below average maximum for the day of the month.

Humidity

I am using 0600 and 1400 as my standard times for the period out of Daylight Saving: while not identical to the BoM standards of 0900 and 1500 looking at my past records suggests that they are ‘close enough’ for this report.  We are not betting our homes on this stuff.

The noteworthy feature appeared to be  how many low readings there were  for the morning reading.  However on comparing to my historic series the average for the morning series (79.1%) is lower than it has been in recent years, but higher than most Augusts 2019-2023.  However the afternoon average (63.8%) is 2% below the average and is lower than all Augusts except 2019 when a rather crisp 61.7% was achieved.

Wind

My basic measure for wind using my Ecowitt station is daily average gust.  On that basis this was a rather calm month.  Way down on both average and last year.

Around the middle of the month I came across this rather strange looking shift in the wind (example shown from the 24th). 

 Marti Goodison commented that this shift to a Southerly flow had been occurring for several days (dropping the temperature as well).  Scanning the daily plots confirmed this to be a fairly common event this month.   I am struggling to work out how to depict it: watch this space in case I sort it out.

Solar

A fairly even pattern this month apart from a couple of very low days.  I wondered whether this indicated cloudiness which neither I nor BoM Airport assess.  However BoM Gabo do include a measure of cloudiness and it shows rating of 8 (total cloud cover) for the afternoon of 9 August (presaging the rain on the 10th) and ratings of 7/8th on the 15th and 25th.

Some flowers

 As should be expected after several very dry months ...

.... Flowers have been a bit light on this Sprinter.  However we (mainly Frances) have come up with a few specimens.  We begin with a walk on the path through the Davic Creek Heath.

The most obvious flowers were Hakea decurrens.

Here showing the definitive nuts.

Some were white as well as thecommon pink.

Dillwynnia sericea

Hybanthus veronii

Acacia suavolens (I think)

Hardenbergia violacea

Epacris impressa

Comesperma ericinum

We also went to the Narrows Car Park looking for Nankeen Night Herons, finding 5 of them, mainly lurking in the Pittosporum undulatum.

On Sunday we went down Old Betka Rd looking for an unusual Acacia, on which we failed.  We did locate a Platylobium parviflora (formerly P. formosum).

Ans Daviesia latifoilia.