I never know when shall I use: "varm" or "varmt"
'varm' is for masculine/feminine, 'varmt' is for neuter. 'det' is neuter in this case, so you should use 'varmt'.
Thanks. I was trying to match the gender of dyna by mistake
Dynen is feminine? If so, why does "varm" have a "t"?
As mentioned above, it is agreeing with the neuter "det"
In this case "warm" is an adverb not an adjective
I have to disagree. It is an adjective modifying the pronoun "det".
Dyne eller dyna?
Dyna. It is the definite form of the feminine noun, ei dyne.
You can say dynen, as a masculine noun = en dyne, dynen, flere dyner, dynene.