first time using a heat mat just a couple quick questions

I'm running my seed setup before anything goes into it to get an idea of where I'm at. After 2 hrs of one 4ft t5, the heat mat, and a temp being monitored in and outside the dome I have a humidity of 90% and temps reaching 90 degrees inside. I kno this has gotta be a lil too much heat for new seeds, so would anyone have suggestions to bring the temp down about 10 degrees without having to go buy a thermosta?

B ack up the light and take the dome off.

So there is no need for tht high of humidity wit seeds? in my previous grows i did more cloning and the high humidity helped

Temps outside the dome r 68f and 45%

My humidity is even lower (25%-30%) when I start out seedlings. I've never used a heat mat or dome. Low humidity is generally never a problem, just high humidity.

Humidity is to keep clones from loosing moisture as they have no roots. The mat will keep the seed and root warm. I assume its a plant heat mat?

Yes its a plant seed mat I will run it without the dome and see wht temps r line after

Perhas an idea to use an anologue timer for the heat mats, half hour on half hour off throughout the day.
My system monitors the effect of the heat mats by means of the pot temperature, but turns them off regularly once activated because if they are continuously powered they become too warm simply.
Not only does it warm up the pots too much imo it also aid in heating up the air temperature, because generally heat mats are able to warm up to like 30 / 35 degres (87f / 95f).
And some even go higher.

I run mine on a thermostat at 78.

Thanks guys