00:00 - Hi I'm Jeff Harding I'm a licensed battlefield guide at gettysburg but I'm here today

00:03 - in the capacity as a historian discussing the weather

00:06 - during the battle

00:07 - and I'm John nice penn state meteorologist we are at the eternal light peace memorial

00:12 - overlooking part of the battlefield

00:14 - from day one

00:15 - said Stuart ground

00:16 - oh kill where the peace light is located

00:18 - gives you a complete view sure shed

00:20 - to examine every aspect of the battle

00:22 - on the first day gettysburg

00:23 - now interestingly enough

00:25 - you have two huge armies about ninety three thousand union soldiers

00:28 - seventy thousand confederates

00:30 - kind of clamoring for one another

00:32 - the union army trying to keep the confederates

00:34 - away from Washington d c Philadelphia Baltimore

00:36 - and as these troops gradually move northward

00:39 - they are going to kill clash of gettysburg as much as anything

00:42 - the ten roads that lead here bring them together

00:44 - and that coming together will happen at seven thirty in the morning

00:48 - just west of gettysburg on the chambersburg pike

00:50 - when the first shots of the battle were fired

00:53 - and remember

00:53 - nobody planned to fight at gettysburg this is

00:55 - what historians would call a meeting engagement

00:58 - most of us the guide here goes for collective referred to it is happening

01:01 - accidentally on purpose.

01:03 - We do have weather information from here in

01:05 - gettysburg courtesy of professor Michael Jacobs

01:08 - who took observations during the battle three times a day he told us

01:11 - at seven that morning the temperature here was seventy two

01:14 - it had only risen to seventy six

01:17 - by two in the afternoon largely because it was mostly cloudy that day Jacobs told us

01:21 - about one hundred percent cloud cover most of the day

01:23 - although some of the soldiers told us there were some

01:26 - breaks of sun

01:27 - there was very little wind

01:28 - on day one of the battle

01:30 - there was no reported precipitation

01:32 - here in gettysburg

01:33 - the one thing that the soldiers told us

01:36 - is that it was uncomfortable on day one

01:39 - now you might think there's a

01:41 - that's a bit of a conflict because seventy six degrees doesn't sound all that hot

01:45 - the average high in this

01:46 - part of Pennsylvania

01:47 - in early July is eighty five

01:50 - now that seventy six doesn't represent the high temperature for the day

01:53 - because that was only at two o'clock it probably went up a couple of degrees but

01:57 - probably didn't get to eighty

01:59 - but they complained

02:00 - that it was is humid

02:02 - and we have a lot of accounts John that's for sure and the interesting thing is we

02:05 - have looked at these accounts and decided that

02:08 - the armies were equal opportunity to complainers

02:10 - there's no doubt

02:11 - that both sides leave accounts of how much they're suffering

02:14 - from the weather circumstances that

02:16 - day

02:16 - certainly in the morning but especially in afternoon

02:19 - and in the afternoon the very ground where all

02:21 - one is where confederate troops some of them

02:23 - had been on the doorstep of Harrisburg

02:25 - threatening that city

02:26 - when the recalled in this direction as the armies have begun

02:29 - to come together

02:30 - and when the battle started they're coming in earnest now

02:32 - and you're going to have a tremendous fight here

02:34 - and these guys are coming in during the heat of the day

02:36 - but seventy six

02:38 - how hot really

02:39 - did that seemed to the soldiers were their council lead you to believe

02:42 - it was terrifically hot

02:43 - but looking at that number I wonder

02:45 - and I realized again

02:47 - I need a meteorologist

02:48 - who's got more sources to get us to the ground truth

02:50 - and it's funny Jeff mentions Harrisburg because.

02:53 - Harrisburg's thirty five miles to the northeast of gettysburg

02:56 - and

02:57 - during some of these sultry summer days

03:00 - that thirty five miles really doesn't make much of a difference and in fact

03:03 - we simply looked at weather observer data

03:06 - from Harrisburg

03:07 - and move that data here to gettysburg and

03:09 - the weather pattern that dominated the battle

03:11 - suggest that we can do that and if you do that Jeff if you take

03:15 - the humidity data

03:16 - from Harrisburg

03:17 - and turn it into a measure we meteorologist called the dewpoint

03:21 - your fire find out right away

03:22 - that it was

03:23 - extremely

03:24 - humid even on that first day

03:26 - sultry

03:28 - and oppressive and that's

03:29 - why the soldiers complain not because of the temperature

03:32 - which likely didn't get to eighty

03:34 - but because the combination of temperature and particularly the humidity part of it

03:38 - left them

03:39 - sweating literally all day

03:41 - if they're at rest for spending periods of time

03:44 - then maybe it doesn't feel so bad to them but

03:45 - boy if they're out there exerting themselves

03:47 - now you really begin to feel this

03:49 - and this was important ground and d John because this

03:52 - is where the action will begin again in the afternoon

03:54 - as confederate forces are coming in

03:56 - from north of us the ones that have been up towards Harrisburg

03:59 - they're going to come in from northeast of us from the York vicinity

04:02 - and you got confederates coming in from the west as

04:04 - well and the union boys are coming up from the south

04:06 - the northerners coming up from the south can you imagine

04:08 - but they've been

04:09 - guarding

04:10 - Baltimore Washington Philadelphia

04:12 - so it's a natural thing and again those roads will bring them together here

04:15 - so much so that this turns out to be one of the

04:17 - worst battles to occur in the united states civil war

04:20 - if you look at a casualty wise

04:21 - it's a tie twelfth bloodiest battle of war

04:23 - but if you look at it percentage wise the number of casualties

04:26 - for the number troops engage

04:28 - this is the bloodiest battle

04:29 - of the entire

04:31 - civil war

04:32 - and just closing with a weather thought.

04:35 - All

04:36 - since the time of the battle

04:38 - the weather data suggested

04:40 - that it was only in the seventies here in

04:42 - gettysburg on day one of the battle

04:44 - that doesn't sound like a very big number for the middle of summer in Pennsylvania

04:48 - but when you factor in the humidity

04:50 - we now understand better why soldiers complained so much

04:53 - about weather conditions on the first day.