DD 8.5mo waking at 3.30am on the dot...every night

[MedicalEd]

I can't figure out what is causing it. The temperature in her room does not change, there are not noises at that time of night ect.
If I leave her she chats for anything up to two hours before she starts crying and I go in (I cannot do CC).
She is breastfed but I am not sure she is always hungry. She has gone a couple of nights until 4.30am/5am so I know she can do it.
The only difference I can tell on those days/nights was that it was raining really hard all night.
I can't do much about that but I have put some white noise on in her room to try and replicate it but she is still waking at 3.30am.
How do I break this habit?

I would love to know this too, my DD (10 months) is exactly the same except slightly later (4am ).

I have also introduced some white noise but nothings changed yet. Lets hope we get some good ideas soon x

As if to prove me wrong, she woke at 1.30am last night.
Slept through all the fireworks though