Excessive overuse of Arcane magic causes Humans to age faster.
Something about Bio-Mechanical titan constructs, and lasting effects of the Curse of Flesh.
Assuming Jaina was around 18-20 at the time of the third war, Not unreasonable considering she was a young woman, she would be late 30’s to Early 40’s.
Not entirely sure on the number, but she Isn’t a Senior. Just artificially aged due to the Arcane.
Hahah responding to an almost 2 year old post to agree with someone but not add any new information. How does it happen?
Holy Cannoli, I just noticed this Necromancy.
I did the calculations some time ago:
Damn. I had a pretty solid estimate. 
So most of the greying in her hair is coming from overuse of magic, and not from Age.
Thanks Grymauch!
It was pretty clear in that book (I forgot the title) where Garrosh destroyed Theramoore with a mana bomb that her hair turned white out of shock.
There’s nothing in canon about magic making hair age prematurely — Khadgar was an unique case; he was cursed/drained, that’s why he looked like a 80-year-old despite being about 18 years old in the Second War.
The others can give a more exact number on Khadgar. But the point stands.
I didn’t know that.
Well, it explains why this early thirties arcane mage is grey, lol !
The greying of her hair is not due to overuse of magic, but due to the affects of the Mana-Bomb that destroyed Theramore.
She essentially took an Azeroth Nuclear bomb (indirectly) to the face as Rhonin closed the portal to save her from it. Theramore was destroyed, and all the people in it were essentially burned to ashes, and in the case of Jaina’s Gnomish Apprentice, burned to ash so swiftly that she even retained her form until Jaina touched her and she disintegrated before her.
Edit Also, Khadgar is only about 10-15 years older than Jaina and he only has Grey Hair because he was prematurely aged via curse by Medivh when Khadgar and Lothar killed Medivh to try and halt the Dark Portal during the events of Warcraft 1.
Remember Theramoe, always. And make sure to kill as many horde scum as you can.
Young.
Enough.
The Archmages of Dalaran, and many previous members of the Council of six from the First and Second War aged prematurely. Archmage Antonidas rather famously never learned how to Shave.
There are a few people this rule DOESN’T affect thought.
Medivh and the other guardians don’t feel the faster aging because they’re empowered by the other guardians.
Khadgar is an Odd case, HE was cursed to be an old man, then his youth was restored by the Narru to the point he was at WHEN he was cursed. So even though he was a fully grown adult, he would’ve looked like a young apprentice again.
However continued use of magic whitened his hair, and now He’s just… Odd.
He clearly has the mind of a Senile old man. But the body of a young Wizard, but his hair is grey… It’s complicated.
ALSO
This is absolutely true, and I failed to acknowledge it.
As other have said, she is in her 30’s. Still quite young. It is just the crazy spells she used have taken a toll on her.
Ok it is confirmed .
Necro Lord Covenant has arrived
Jaina Proudmoore has grey hair because of magic, sure, that’s some of it. But the main reason she has grey is because of one person… Kinndy Sparkshine…
“The shape looked like a child at first, which was what drew Jaina’s eye. The children had all been evacuated safely. Who—
And then she knew.
Jaina stood, barely breathing, wanting to look away but unable to. Slowly, jerkily, her feet moved, almost of their own accord, taking her to the body.
Kinndy lay face down in a still puddle of her own blood. The crimson stain had tainted her pink hair, matting it, and Jaina realized she wanted to plop Kinndy into a hot bath and help her scrub herself clean, get her a fresh new robe—
She fell to her knees and placed a hand on the girl’s shoulder, to turn her over. Kinndy’s body crumbled into shining violet dust.
Jaina screamed.”
Kinndy Sparkshine was Jaina’s apprentice and also a Gnome with pink pig tails. She was very young and constantly challenged both Jaina and Kalecgos on their magical knowledge. Jaina came to really enjoy having Kinndy around.
Kinndy’s death pushed Jaina over the top when Theramore fell. Its why Jaina lost it and her hair turned grey.
I hope Jaina meets Kinndy in Shadowlands.
Come again?
Like around in her late 30s to early 40s.
Almost as old as this thread.
She’s young enough to look at, and far too old to see.
Octonoozle is an awesome name btw. We should change Lord Stormsong’s name to Octonoozle.