Let me give you my 5 cents.The horrible weather is one of the reasons I'm not going to dive locally much. The other reason is, there's nothing interesting to see around here. I fell in love with diving because of reefs, all the little critters in there, and big critters like sharks and dolphins. Here we just have maybe 5 dive sites total, with uninteresting average sized gray fish if you're very lucky, and small sunken boats. So I have no reason to invest into anything that would help me dive locally. And buying a drysuit for tropical diving is way too much.
1. I'm not convinced Lithuania is so bad, maybe for a beginner, but you won't always be a beginner . Talk to local guys, check quarries, check further around (you have amazing diving relatively close in Poland).
2. Drysuit is not an overkill in any terms other than cost and it's subjective. I dive a lot in Canaries and Gozo which we keep going back to and always happy to have a drysuit with us. With time you're going to spend longer and deeper as you progress and 24C water is not that warm. And drysuit cannot be too hot - it's actually much colder than a wetsuit if you don't take any undies. It's just a watertight bag, with ZERO thermal protection, the protection comes from whatever you put on under the suit - giving you much better control over insulation levels you want and making you much more comfortable and safe (!) as you progress.
Not to overdo it, but drysuit has two safety aspects wetsuit doesn't - when you're warm you're improving the degassing to normative levels and push the DCS risk further away, and it can serve as emergency bouyancy source (for whatever reason).
Anyway, apologies for boring you, in the end the drysuit boils down to cost and affordability.