NH Summer/SH Winter 2023 Discussion Thread

The Winter Conundrum: June 1st, June 21st, or Other?
( Source: Weatherzone )

You’ve probably heard that winter is finally here, or less likely, it’s ‘just around the corner’. And you’ve probably felt it too, if you happen to be in the southern or eastern part of the country, like when we saw a QLD town dropping below freezing, cold fronts crossing the country, or thundersnow gracing the alps.

Turns out, nobody really agrees on when the seasons start and end. Here in Australia as well as New Zealand, Pakistan and Russia, people tend to group whole months together and call them seasons, as defined by our 12-month calendar. These are known as the “meteorological seasons” and are based on the annual temperature cycle. In Australia, for example, June, July, and August are the coldest months of the year.

Winter: June 1st – August 31st

Spring: September 1st – November 30th

Summer: December 1st – February 28th/29th (depending on leap-year)

Autumn: March 1st – May 31st

The Aboriginal people of D’harawal, the nation that encompasses part of the Sydney basin and slightly south, define their own six seasons based on the seasonal adapting of flora and fauna. Interestingly, Aboriginal nations around the country have many different seasonal interpretations, ranging from 2-6 distinct seasons.


In India, the seasons are similar to the meteorological seasons, but monsoon considerations have been inputted.

Winter: December 1st – February 28th/29th (depending on leap-year)

Pre-monsoon: March 1st – May 31st

Monsoon: June 1st – September 30th

Post-monsoon: October 1st – November 30th

A common method for season determination in China is using average temperature thresholds to define seasons.

Winter: Period when temperatures are below 10°C on average

Summer: Period when temperatures are above 22°C on average

Yep, only two seasons. This means that locations with extreme climates, such as Tibet, can have one season year-round, based on this definition.

Similarly, in countries like Sweden and Finland, seasonal changes are a blurry line thanks to their proximity to the north pole. They are defined by the “permanent” exceedance of certain temperature thresholds. In this case, permanent is 5-7 days.

Winter: Temperature permanently below 0°C

Spring: Temperature permanently above 0°C

Summer: Temperature permanently above 10°C

Autumn: Temperature permanently below 10°C

This means that seasons begin at different times in different parts of the country. Huh?!

A definition that dates back a couple thousand years is the “astronomical seasons” and is the most common seasonal definition currently. The seasons start on the longest day of the year (summer solstice), shortest day of the year (winter solstice), and the days when daylight and darkness are of equal length (equinoxes).
Winter: June 21st – September 20th

Spring: September 21st – December 20th

Summer: December 21st – March 20th

Autumn: March 21st – June 20th

Like the meteorological seasons, they are grouped into three-monthly periods, though they are offset by about 20 days. They use the exact times that the sun is overhead at the Tropic of Capricorn and Tropic of Cancer latitudes (23.5°N and 23.5°S) as the beginning of summer and winter respectively, meaning that the exact dates fluctuate from year to year, but only slightly (between 2-3 days offset from the 21st of the respective months).

To evolve this further, we can look at the traditional Chinese method of seasonal determination – the “lunisolar seasons”. This definition centralises the start of the seasons around the solstices and equinoxes.

Winter: 7th November – 3rd February

Spring: 4th February – 5th May

Summer: 6th May – 7th August

Autumn: 8th August – 6th November

It may seem like a random pick of dates, but in the middle of each of these dates are indeed the solstices and equinoxes.

A similar concept is used in the traditional Irish Celtic calendar, which marks the day where the sun is highest in the sky as “midsummer”, as suggested in Shakespeare’s A Midsummer Night’s Dream, set on the summer solstice.

Winter: 1st November – 31st January

Spring: 1st February – 30th April

Summer: 1st May – 31st July

Autumn: 1st August – 31st October

A certain date should be familiar here – October 31st, or Hallowe’en. Yes, the origins are from the Celts – Hallowe’en marked start of the ‘dark half of the year’ and welcomed the harvest marking the end of the growing period. The darkness was portrayed as the breaking down of the spiritual and physical world, so people would dress up to ward off ghosts.

So, take your pick! So many different definitions of seasons have arisen for as long as humans have been around. The foundation of all these definitions comes down to two things: weather and daylight.

This year’s winter solstice will occur at 12:58 am AEST on Thursday, June 22. From then until the next solstice, days will start to get longer. Read more about the upcoming solstice here.

Looks like a classic North West Indian Ocean Cloudband/rain event about to inpact WA
( source: Weatherzone )
Wet Weather Spreading Over WA:

Cloud and rain will spread over a broad area of WA during the next three days, with some parts of the state likely to see around a month’s worth of rain in one day.
June is not typically a very wet time of year over northern and central districts of WA. In a typical June, these parts of the state would usually see about 10 to 20 mm of rain.
Some parts of the state could see that much rain over the next few days as moisture from the Indian Ocean fuels a large cloud band over the state.
The animation below shows cloud and rain spreading over WA’s Pilbara district from the northwest late on Monday morning.

Onslow Airport’s 24.6 mm during the 24 hours to 9am on Monday was more than half its monthly average and the heaviest June rain in four years. Thevenard Island’s 29.2 mm during the same period was close to 80 percent of its June monthly average.
The satellite image above also shows a band of cloud approaching the southwest of WA on Monday morning, which indicated the location of an approaching cold front.
Over the next two-to-three days, the cold front in the southwest will interact with the mass of cloud streaming in from the northwest to produce widespread rain across WA. The map below shows how much rain one computer model is predicting over WA between Monday and Wednesday this week.

The moisture from this system will also spread further east and fuel rain across SA on Wednesday and Thursday, and parts of southeastern Australia from Thursday.
There are also early indications that another round of widespread rain could affect parts of western, central and southern Australia towards the end of this week and early next week. Weatherzone’s meteorologists will be keeping a close eye on this developing system and providing more updates in the Weatherzone news feed later this week.

So after the absolute crap spring of 2023, June has done a complete 180 and now looks like it will dethrone 1976 as the hottest June on record.

June 1976 averaged 25.5c, and 2023 so far is averaging 25.1c with 11 days still to go. And those 11 days have forecast highs of 27-33c.

Canberra Felt Like -10C This Morning ( yeah right... )
( source: Weatherzone )

Canberra just endured its coldest morning so far this year, with the temperature feeling like -10ºC shortly before sunrise.
A combination of clear skies, relatively light winds and a very cold air mass allowed temperatures to plummet across the ACT on Monday night into Tuesday morning.
The graph below shows how the night played out in Canberra. The temperature was sitting at 1.2ºC at midnight and the first sub-zero reading came in shortly after 1am. Then, after a few more hours of nocturnal cooling, the air temperature plunged to a low of -5.6ºC at 5:51am, which was Canberra’s lowest temperature so far this year.

The graph above shows the raw air temperature observed at Canberra Airport, which is measured inside a Stevenson Screen at a Bureau of Meteorology weather station. However, the temperature would have felt even colder than this for anyone that was outside and exposed to the wind and dry air in the early hours of Tuesday morning.
While the raw air temperature in Canberra dropped as low as -5.6ºC on Tuesday morning, the ‘feels like’ temperature got to a frigid -10.4ºC shortly before 6am.

While temperatures like this are not uncommon in Canberra during winter, no other Australian state capital city has come close to getting this cold. The lowest temperature on record in another state capital was -2.8ºC, which has happened in Melbourne and Hobart.

Canberra will have another bitterly cold morning on Wednesday, with the temperature expected to drop to around -5ºC or -6ºC once again. Fortunately, the city’s minimum temperature will be closer to 0ºC on Thursday.

Bis repetita. Pathetic.

First 30C for Finland this summer. Highest was 31.5C in Kankaanpää, Western Finland.

Turku did not hit 30, but Helsinki and Tampere airports did. Can't blame us for not trying, highs the past days have been 29.7C, 29.9C, 29.3C. 29.1C and 29.4C.

Congrats! Today was the day of the thresholds,, with the first 40°C+ temps of the summer in France, with 40.2°C in Sartène, Corsica.



Btw strong supercell in the Southwest. Also strong storms in the Norffff, with e.g. 100 mm in Armentières near Lille.

Exceptionally cold day in Northern Victoria at 1.00pm in the afternoon.... I'll have to look up what the June low max records are in these low altitude towns.



Sa expected,the dreaded 9.00am reset has cruelled some of the record cold max temps from yesterday.
Shepparton - 6.7c at 9.00 ( still a new low max record for the Airport site )
Tatura - 6.5c at 9.00am
Kyabram - 6.2c at 9.00m
Yarrawonga 7.4c at 9.00am

I wasn't aware of a correlation between spring rainfall and summer humidity, but I could be wrong.

I just imagine that any of that excess rainfall will have evaporated long before that heat arrived, especially in the strong sun this time of year.

Only thing I can think of the rainfall caused a lot of plant growth, which are now transpiring and increasing humidity, but that's usually not a consideration for airports which are so far removed from natural vegetation.