What does your toddler wear to bed/sleep under?

[YukoandHiro]

My just turned 3yo moved into her big bed from the cot about a month ago. The transition has gone smoothly, except I can't seem to get him night time and temperature right.
I know it's been a hot few weeks but she sweating a lot in the first hours of sleep and then getting cooler later and wakening.
She goes to bed in PJs (shorts and t shirt ones on warm nights) and has a 4 tog duvet. She still wears a night nappy and I guess that keeps heat in too.
When she was in the cot she had the same bed wear plus a sleeping bag and she didn't seem to sweat as much then - only on hottest nights.
So she's either kicking the duvet off hot or I peel it back if she's sweaty, then she cools down and feels chilly and she hasn't worked out how to pull it back over herself yet. She likes something covering her when she first goes to sleep.
Any tips on thin duvet alternatives in summer? What do you all use?

Do you have the windows open?
You could use a cellular blanket instead of a duvet

You can get 1tog duvets

Dd likes just an empty duvet cover over her on warm nights. She can't sleep uncovered

We don't have windows open apart from on the hottest nights - we're a third floor flat so even though we have safety catches on the shutters I prefer it shut in her room if it's not a heatwave.
I probably am just over dressing her, but she does then get cooler later on.
I've just gone in now and had to change both her pillowcase and her t shirt as she was so damp but had cooled down so was uncomfortable.
I will buy a 1 tog duvet and a light blanket and try those instead.

If it's very hot maybe ditch the PJs

Pull up, short pyjamas and a cellular blanket

Resurrecting this as STILL haven't solved the issue. She wears slim cotton PJs (short sleeved if warmer) and have also swapped for a 1 tog duvet.
She's definitely a "hotter" person than me but, to me, her room is chilly the last few nights. But even if her body is just nice and toasty and dry her hair will be dripping with sweat within 10 mins of falling asleep. Then sometimes by 11pm ish (when we're going to bed) she'll have kicked off her covers to cool down - or we'll have peeled them back - and will have dried off and be too cool and call for us. She doesn't sweat again then, just seems to be in earliest hours of sleep.
I'm going to try a wool pillow in case her pillow is overheating her head.
Any other ideas? She seems 100'perncent fine in herself, isn't ill, hasn't lost appetite etc - I'm not worried about her, as such, just want to make her comfortable all night!

Should also add that her room is the most humid in the house (damp Victorian). I run a dehumidifier in there every day in autumn/winter but wasn't planning to crack it out yet....

(Flip side to all this is with all the sweatyness her eczema has cleared up lovely!!)