All Time Low - Remembering Sunday Lyrics Meaning

So Alex straight up said what the song was about. It's about his ex girlfriend, Meg Frampton from Meg and Dia, and no, she did not die. I'll break it down for you.

He woke up from dreaming and put on his shoes
Started making his way past two in the morning
He hasn't been sober for days
Leaning now into the breeze
Remembering Sunday he falls to his knees
They had breakfast together
But two eggs don't last
Like the feeling of what he needs
Now this place seems familiar to him
She pulled on his hand with a devilish grin
She led him upstairs, she led him upstairs
Left him dying to get in

He wakes up from a dream about the girl he loves, who has left him. remembering the good times they spent together. He is hungover because he can't tolerate the pain of her ghosting him. She didn't believe in love, but she slept with him and dated him anyway without realizing how much he cared about her. She felt guilty, and rather than sit down and break up with him, she left on a plane to start a new life without telling him. After this happens, he begins drinking and recounts the memories of her that he had in his dreamz he is starving for love and empty.

He wakes up alone the morning after she leaves and goes to her house but someone new has moved in and he asks neighbors where she has gone, they tell hi she moved away. He is in disbelief and wants to go in and find her there like normal but they turn him away.

Forgive me I'm trying to find
My calling, I'm calling at night
I don't mean to be a bother
But have you seen this girl?
She's been running through my dreams
And it's driving me crazy it seems
I'm gonna ask her to marry me

Even though she doesn't believe in love
He's determined to call her bluff
Who could deny, these butterflies?
They're filling his gut
Waking the neighbors, unfamiliar faces
He pleads though he tries
But he's only denied
Now he's dying to get inside
The neighbors said she moved away
Funny how it rained all day
I didn't think much of it then
But it's starting to all make sense
Oh I can see now that all of these clouds
Are following me in my desperate endeavor
To find my whoever, whoever she may

He is desperately trying to find answers because he is serious and wants to spend his life with her. The day she left, it was raining. Now, back in the present, he realizes that symbolized that the sadness would follow him around as he continues his search for the one, he can't get over her.

Now we are back to the memories and flashbacks to the day she left, this time from her point of view.

"I'm not coming back, I've done something so terrible
I'm terrified to speak, but you'd expect that from me
I'm mixed up, I'll be blunt, now the rain is just
Washing you out of my hair and out of my mind
Keeping an eye on the world
So many thousands of feet off the ground
I'm over you now, I'm at home in the clouds
Towering over your head"

She is feeling guilty. She slept with him, she made him fall in love with her but she's all mixed up and didn't realize what she was doing. She's too scared to break up with him in a civil way, and gets on a plane to run away from her problems and try to forget. She feels free of the commitment, "in the clouds" a reference to being on cloud 9. She's getting over it, and running away. She is telling him that he won't find her, she's flying back home to where she came from, far away from him, currently over his head. She is also above the rain storm, she isn't hurting like he is, because she didn't love him. Only feeling guilty. The rain that is falling on him is merely washing away her memories of him.

He finally realizes she is gone, she left him. So he goes home and stops looking.

It's a pretty clear story but people sure like to read too hard into things and make stuff up. Anyway, that's what it is.