Ways of defining the seasons

[Thunderbolt_]

Since there always seems to be a debate, mainly at the end of every summer and winter, about how the seasons are defined, in this thread I'm going to run over some of the most common season reckonings.

 

Meteorological reckoning

 

The meteorological reckoning of seasons is the one that many of us are familiar with and use on a regular basis. It is used by many Brits and quite a lot of Europeans. The meteorological reckoning is one of the simplest methods of defining the seasons. It basically attaches three calendar months to each season. For example:

 

Spring: 1 March to 31 May

Summer: 1 June to 31 August

Autumn: 1 September to 30 November

Winter: 1 December to 28/29 February

 

Astronomical reckoning

 

The astronomical reckoning is less common here in the UK, but is still used by a fair few, however this reckoning is mainly used by North America. It works on the basis of solstices and equinoxes, therefore the positions of Earth on it's orbit. Very simply a new season will begin when it's respective solstice or equinox occurs. The most common dates for the astronomical seasons are:

 

Spring: 20 March to 20 June

Summer: 21 June to 22 September

Autumn: 23 September to 20 December

Winter: 21 December to 19 March

 

Solar reckoning

 

The solar reckoning of the seasons is virtually unheard of in the UK and most of Europe and North America. However in many East Asian countries, this reckoning is most commonly used. It works in a very similar way to the astronomical reckoning in which it relies on the solstices and equinoxes, but with one key difference - the respective solstice or equinox falls slap bang in the middle of the season. Therefore the usual dates for the solar seasons are:

 

Spring: 4 February to 5 May

Summer: 6 May to 7 August

Autumn: 8 August to 6 November

Winter: 7 November to 3 February

 

Ecological reckoning

 

The ecological reckoning is a bit different to the previous reckonings that I've looked into. This one doesn't really take any interest into Earth's orbit, but instead observes nature. It is also different because it has six seasons, instead of the traditional four that we know of. For example:

 

Prevernal (pre-spring): 25 January to 10 March

Vernal (spring): 11 March to 31 May

Estival (high summer): 1 June to 14 August

Serotinal (late summer): 15 August to 24 September

Autumnal (autumn): 25 September to 30 November

Hibernal (winter): 1 December to 24 January

 

Traditional Irish reckoning

 

The traditional Irish reckoning of seasons is virtually unused today. It was observed in the traditional Irish calendar and works in a very similar way to the meteorological reckoning, though it also seems to be influenced by the solar reckoning too. The one key difference is that this is one month ahead of the meteorological, so each season begins a month earlier. For example:

 

Spring: 1 February to 30 April

Summer: 1 May to 31 July

Autumn: 1 August to 31 October

Winter: 1 November to 31 January

 

These are the five most widely used seasonal reckonings. If you know of anymore, or you have your own way of defining them, then post below!

Edited September 6, 2014 by ScottRichards10

[Summer of 95]

High summer for me is about 10 July to 20 August. During this period it is extremely unusual to get maxima under 15C in England and Wales below 1000ft asl. During late May, June and early July they can still happen, even if most days can be expected to reach 16-23 or so; hence this is early summer. Likewise 20 August up until mid October they can happen, and get increasingly common towards the end of the period. But you can still get 20C or more. This is late summer or early autumn, the choice is yours.

In winter a line is crossed in February after which it is difficult for a dusting of snow to persist through the day, and ice days become rare. Also once this line is crossed in February it isn't unusual to get a 15C day when the sun comes out in England and Wales. Even if nights can still be very cold, after about 15 Feb through to late March is late winter.

Late winter should be distinguished from winter proper. This ends when the above starts, though its start can vary from late November (e.g. 2010) to late December. 1cm of snow can lie for days, ice days occur, and temps over 15C only occur downwind of mountains in cloudy SWly setups. This last feature is important: even in mild winters you only get 15C during this season under the conditions stated above. Not in sunny anticyclonic like in late winter.

Late March to mid May is spring. Anything from air frosts to 25C heat is possible, as is snow though it won't lie for long. Mobile westerlies are at their least frequent, though can still occur.

Mid Oct to the start of winter (varies, see above) is the grim season, often around 10C with cloud and rain and wind. Snow and 20C+ heat are both extremely rare, and the only nice thing about this season is the occasional frosty, foggy spell. These seem rarer and rarer though.

[h2005__uk__]

If you call it Extended summer as well as extended Winter then you are down to 2 seasons!!!

 

Well the old Zambretti Weather Forecaster just has two options - "winter" or "summer", presumably Sep to Mar for the former and Mar to Sep for the latter.

 

Judging from my 26 years on this planet - living in the south-east of England - I'd define the seasons as follows:

Winter: mid/late Nov to end of Feb (main part start of Dec to early Feb)

Spring: start of Mar to late May (main part late Mar to early May)

Summer: late May to early Sep (main part late Jun to early Aug)

Autumn: early Sep to mid/late Nov (main part start of Oct to early Nov)

 

I think the astronomical start of winter is too late to be considered the start of the winter season - my birthday's on 13 December and I wouldn't say that's in the autumn.

[Guest]

When I were't lad at school over 55 years ago, I'm sure we used the astronomical cycles to differenciate between on season and another but in actual fact it does not always work out as simple as that.

 

Winter the onset of winter in weather terms can occasionally be as early as the end of October and reasonably often finish during April; that is if we are going to define winter as being a season with falling snow. Then very often seasons merge into one another - it is often the case, sometimes as early as January when we can get some mild spring like weather, in fact it is said sometimes that winter borrows from spring to pay back in the spring when sometimes we get a spell of Northerlies bringing snow.

 

And if we are to use falling snow as a criteria, we can say that we have some years without a winter at all.

 

We can usually say that summer lasts from June to about the middle of September, though this period is often associated with variable weather with some more settled spells, though it has been known to snow in June in some places and the Scottish Highlands generally get their first snow of the winter during September.

 

The springs and the autumns fit in between these other two as and when they can and can be best described as transition periods between winter and summer and vice versa, though the start of the growing season could usually be described as spring and the loss of leaves from deciduous trees autumn, though this varies on the types of trees but generally it takes to December for most of the leaves to fall.  

[stewfox]

 

Solar reckoning

 

The solar reckoning of the seasons is virtually unheard of in the UK and most of Europe and North America. However in many East Asian countries, this reckoning is most commonly used. It works in a very similar way to the astronomical reckoning in which it relies on the solstices and equinoxes, but with one key difference - the respective solstice or equinox falls slap bang in the middle of the season. Therefore the usual dates for the solar seasons are:

 

Spring: 4 February to 5 May

Summer: 6 May to 7 August

Autumn: 8 August to 6 November

Winter: 7 November to 3 February

 

 

 

Not seen this one before and it has some merit.

 

I think the best would be to move those dates 2 weeks forward.

[Thunderbolt_]

Not seen this one before and it has some merit.

 

I think the best would be to move those dates 2 weeks forward.

 

I agree. It runs way too early, in my opinion.

[Weather-history]

Not seen this one before and it has some merit.

 

I think the best would be to move those dates 2 weeks forward.

Leo Bonacina of UK snow survey fame, suggested this about 100 years ago.

[MP-R]

Not seen this one before and it has some merit.

 

I think the best would be to move those dates 2 weeks forward.

 

I'd second that!

[Mapantz]

I don't see why there has to be a debate on it personally. The MO use the way of 1st to the 30th or 31st so they can keep data tidy and compare it easily to other seasons, that's fine.

Astronomically, that is spot on. Summer ends on the 23rd this year, I see no problem with it.

[Bobby]

For something specific to the UK, from http://weatherfaqs.org.uk/node/179

 

Hubert Lamb identified five 'natural' seasons, which don't perfectly correspond with calendar months. They are defined thus:-

 

High summer:      18th June to 9th September
 Autumn:      10th September to 19th November
 Early winter:      20th November to 19th January
 Late winter:      20th January to 29th March
 Spring:      30th March to 17th June

According to Lamb, these are the important characteristics of each of the five 'seasons' as defined above.

 

HIGH SUMMER [18th June - 9th September]:
High frequency (using lengthy datasets) of similar weather types ... i.e. dry/warm or wet/cool ... in the period analysed by Lamb (late 19th & first-half 20th centuries), years with cyclonic/wet sequences are twice as likely as persistently anticyclonic (A) types ... in other words, in 'high summer', you are more likely to experience an 'unsettled' summer than a quiet, fine one; a common experience! ... depressions tend to be shallow, moving less rapidly than in winter (weak driving polar front jetstream [PFJ]) ... can remain slow-moving for many days ... the fine (A type) summers tend to result from 'offshoots' of the Azores high moving east across southern Britain / northern France ... frontal systems being weak and only of passing concern ... mainly affecting (in their most active phase) the north-west of these islands ... there is a tendency for high cells to move east (progression) and to end up over Germany or Denmark, introducing a warm or very warm S (southerly, Tc) type across central and SE Britain ... such periods are ended by troughs approaching from the Atlantic ... perhaps with a warm-plume advection type ahead ... thunderstorms & heavy rain etc. ... however, occasionally the PFJ is displaced much further south & somewhat stronger than 'summer-time' average (e.g. 2007) ... frequent depressions of an active nature ... plenty of rain ... temperatures near or below average.

AUTUMN [10th September - 19th November]:
First week (10th September onwards) driest of year on average, especially central & eastern areas ... but some years show tendency to a mid-September cyclonic / wet spell ... localised heavy (thundery) rainfall resulting from slow-moving areas of low pressure ... early / mid October can be 'two-faced': often 'unsettled' with rain/showers, but occasionally can give rise to anticyclonic / warm conditions, with southerly weather types lifting temperatures to 'near-record' levels ... between 23rd October & 11th November, strong signal for wet/stormy weather with a sharp reduction in A-type weather; sharp reduction this type last week of October c.f. first week.

EARLY WINTER [20th November - 19th January]:
Lengthy spells of any weather type less likely than 'high summer' or 'autumn' ... any extended types tend to be westerly / zonal /mild in nature ... unusual for type established early in this period to persist to end (or into 'Late winter') ... tendency to a post-Christmas 'stormy' period [recent notable examples 1997, 1998 & 1999] ... in former times, if these were to the south, perhaps associated with significant snow [ but not so much in recent years ] ... circulation type around 'New Year' some guide to type later in winter ... significant correlation [Lamb] between cold weather late December / early January & cold winters overall.

LATE WINTER [20th January - 29th March]:
In 50% cases, 'lengthy spells' evident, but no preference to one type or the other (i.e. as between zonal-mild-windy & blocked/cold) ... coldest winters when persistent blocking highs Scandinavia/Iceland regions (Pc/Am types) ... cold, northerly types tend not to last much more than 5-7 days (and in recent years, not particularly cold anyway) ... mildest winters from high zonality [high NAOI] (Tm or rPm types) ... strong correlation between wet winters & mild winters ... dry/anticyclonic mid-March conditions often extend (persistence of type) for 2 weeks or more ... with right conditions, droughts can be prevalent & potentially severe, depending upon precipitation totals earlier.

SPRING [30th March - 17th June]:
Least likely to have extended 'runs' of similar weather ... changeability from day-to-day marked ... N & E types fairly frequent (high pressure anywhere from NW to NE), especially second-half April ... 'late' snowfalls not unusual (even in these days) due northerly outbreaks / polar lows or troughs ... May often brings quiet/dry with increasing chance of extended periods A-type.
[ Based on "The Climate of the British Isles", Longman, 1976 & Lamb's original work.]

 

[Lauren]

Not seen this one before and it has some merit.

 

I think the best would be to move those dates 2 weeks forward.

 

I agree.

 

Personally when I start to think the seasons are starting are as such:

 

Spring - when the dafodill come out and you can go outside without layers on. Usually March - Beginning of June ish.

Summer - when the evenings stay light past 8pm and the sun feels hot on your skin. Usually beginning of June onwards until mid September.

Autumn - When the nights have a chill to them every night and the nights get dark around 8pm. Usually mid September until end of November.

Winter - the layers go back on, the heating goes on and you go to work and come home in the dark. Usually Beginning of December until end of February.

 

By my personal judgement, solar reckoning fits in with that. I'd say based on usual, anticipated weather, that solar is most accurate.

[Thunderbolt_]

I've just added the ecological and traditional Irish reckonings to the list.

Edited September 6, 2014 by ScottRichards10

[stewfox]

I agree.

 

Personally when I start to think the seasons are starting are as such:

 

Spring - when the dafodill come out and you can go outside without layers on. Usually March - Beginning of June ish.

Summer - when the evenings stay light past 8pm and the sun feels hot on your skin. Usually beginning of June onwards until mid September.

Autumn - When the nights have a chill to them every night and the nights get dark around 8pm. Usually mid September until end of November.

Winter - the layers go back on, the heating goes on and you go to work and come home in the dark. Usually Beginning of December until end of February.

 

By my personal judgement, solar reckoning fits in with that. I'd say based on usual, anticipated weather, th

at solar is most accurate.

 

I think you need fixed dates , some dafodill can come out in January in far south west.

 

I would have 

 

Spring

 

18th Feb to 17th May

 

Summer 

 

18th May to 17th August

 

Autumn 

 

18th August to 17th November

 

Winter 

 

18th November to 17th February

[cheeky_monkey]

In Alberta Canada seasons are as follows

 

Winter = Oct 25th - May 1st

 

Spring = May 1st - June 22nd

 

Summer = June 23rd - Sept 15th

 

Autumn = Sept 15th - Oct 24th

[cheese]

Do you think winter really lasts that long in Calgary? Average high in April is 11.2C and 16.3C in May, so by late April it must be getting fairly mild.

[sundog]

Spring: 1 February to 30 April

Summer: 1 May to 31 July

Autumn: 1 August to 31 October

Winter: 1 November to 31 January

 

 

The irish reckoning as posted in the opening post.

 

Yes that is exactly what i was thought when i went to school here back in the 80s and i used to still think that way well into the 90s. Now i go by the

Meteorological reckoning.

 

As an aside I always think of the 2 big changeover points of the year as being  mid April and mid October

[cheeky_monkey]

Do you think winter really lasts that long in Calgary? Average high in April is 11.2C and 16.3C in May, so by late April it must be getting fairly mild.

I lived in Calgary for nearly 3 years..each year it was snowing to the end of April even into early May on occasion..of course it can be warm in April as well but just as likely to be cold and snowy...also more snow falls on average in April than it does in February.

Edited September 10, 2014 by cheeky_monkey

[March Blizzard]

Spring: 1 February to 30 April

Summer: 1 May to 31 July

Autumn: 1 August to 31 October

Winter: 1 November to 31 January

 

 

The irish reckoning as posted in the opening post.

 

Yes that is exactly what i was thought when i went to school here back in the 80s and i used to still think that way well into the 90s. Now i go by the

Meteorological reckoning.

 

As an aside I always think of the 2 big changeover points of the year as being  mid April and mid October

 

I struggle to put February in Spring and November in winter. November might have slightly less daylight than February but nowhere near enough to compensate for the much milder conditions typical of the month. November can be very chilly but February can be downright cold, to the point that a very cold November wouldn't be too far off an average Feb. August in Autumn doesn't look right either. In fact, the only season that I could kind of agree with is Summer.

[damianslaw]

For me its a case of how things 'feel' overall in terms of mother nature and the atmosphere, rather than what the weather is doing - as it is often a contradiction.

 

For example, the first half of September always feels like autumn, thanks to rapid loss of daylight, the subtle changes in leaf colour, appearance of fruits and fungi etc and those hazy skies with heavy dues and mists in the morning. However, rarely does the weather feel like true autumn, it is often an extension of summer weather, often warm dry and mellow.

 

Late November also is a contradiction, definitely feels like winter, its nearly as dark as the winter solstice, overcast dark skies and little sunshine make for a mid winter feeling with everything stark and bare, however, rarely does the weather produce mid winter conditions (yes there have been exceptions) but more often than not the atlantic is ruling the roost and temperatures can easily be higher than late March/early April.

 

Late May/Early June always feels like summer, sunshine and light levels nearing their yearly maxim, everything growing in a frenzy under a very strong sun, yet the weather can be distinctly chilly and hardly high summer like - again there are exceptions.

 

The periods for true seasonal feel and weather are quite short in my book as follows -

 

Autumn -  mid October to mid November. Peak of autumn last week of October.

Winter - mid January to mid Feb. Peak of mid winter last week Jan.

Spring - mid April to mid May Peak of Spring last week April

Summer - mid July to mid Aug peak of summer last week of July

 

There is a long time lag for these 'peak' periods occurring long after the start of each season as categorised meteorologically and astronomically speaking.  Weatherwise its always a slow transition into and out of each new season often with many stuts and starts..

Edited September 13, 2014 by damianslaw