Weather conditions have altered the outcome of historic battles and even entire wars. A famous example is that of Napoleon’s defeat in cold, frozen, Russia, in December 1812, and mirrored years later during the second World War with the retreat of the Nazis from the motherland.

But what about the 1916 rebellion in Dublin, when the Irish Volunteers took to the streets to brave bombs and bullets, and declare Irish independence from the British Empire? Did the weather contribute to the outcome during that monumentally important week in Irish history?

Missing meteorological records

To establish those details one could turn to the weather records from the time.

However, in 1916, Dublin’s meteorological observations at Trinity College ceased for a period of almost one month, leaving us with no official records of weather.

Since the mid-19th century some of the earliest meteorological observations in Ireland had been taken at Trinity College Dublin. Here daily measurements of atmospheric properties such as temperature, pressure, wind speed, cloud cover, and precipitation were recorded.

An entry written by meteorological observer S.A. Clarke in the remarks section of the records on Easter Monday April 24th 1916 states that ‘owing to the disturbances in Dublin the observations were not taken from the 24th to the end of the month’.

Since Trinity College represented a strategic point in the city, as soon as violence began that day the university was quickly defended by students and graduates, as well as soldiers stationed there from Dublin Castle.

In fact the hiatus in the records lasted beyond the end of April, until weeks later on May 18th, when an entry in the records book reads “owing to the rebellion in Dublin the observations were not taken in at that time”.

Indeed, a common manifestation of civil unrest is the often necessary abandonment of otherwise regular systems of societal maintenance and observation. In this case the ceased meteorological observation leaves us with no official weather records for this important event in Irish history.

Historical weather detection

To understand what the weather was like when the volunteers took arms, without independent weather observations it is necessary to refer to literature from that time, in a process of historical weather detection.

In his book The Insurrection in Dublin, where a daily account of the rebellion is provided, Irish writer James Stephens presents some clarity on the matter.

No remark on weather is provided on Easter Monday, presumably due to the overwhelming anxiousness and focus on the sudden events, but on Tuesday he describes “a sultry, lowering day, and dusk skies fat with rain”.

That evening “at eleven o’clock the rain ceased, and to it succeeded a beautiful night, gusty with wind, and packed with sailing clouds and stars”.

Wednesday he describes, “this morning the sun is shining brilliantly”, later writing that “it was a delightful day”.

Thursday night “was also calm and beautiful” and Friday morning “the sun is shining, and the streets are lively but discreet”. Again on Saturday “the sun is shining”.

He later writes that “it is astonishing that the weather should be so beautiful”.

A week of fine weather

So anecdotally, it appears to have been exceptionally mild and sunny for the time of year. This can of course occur in April, if the country is dominated by the presence of a high pressure system; that which provides Ireland with warm summer days characterised by clear skies. This suggestion is reflected in some photographs taken during Easter Week, which show bright days, with dark, well-formed shadows.

Author of Dublin 1916 – The siege of the GPO, Claire Wills, says "the weather was unusually mild with very little rain, meaning the fire at the GPO could get out of control".

So in this sense the fine weather worked against the volunteers, with rampant fire forcing evacuation of the GPO on the Friday of Easter week. This subsequently forced an early surrender.

It may have been the case that in poorer - more typical - Irish weather, the outcome of the rebellion would have been somewhat different. Perhaps in rainy conditions, the fire at the GPO would have been extinguished earlier, and the volunteers stood longer, ever so slightly altering the shape of the Irish story.

Who knows. History has its own way.

• Dr Conor Purcell is a postdoctoral researcher at University College Dublin's Earth Institute. He has specialised in both past and future climate change. He can be found on twitter @ClimateGuruNet and some of his other articles at cppurcell.tumblr.com