Electricity 220V, EU plugs,
Weather: End of May should be (usually) nice and quite warm, but weather at the seaside is unpredictable so be prepared if rain, or cold wind appear.
Currency PLN, in most places all major cards are acceptable, there are also change offices in Wrzeszcz and Old Town, there are also cash machines available at various places
Mobile phones and mobile internet – roaming according to EU regulations
WiFi at University – eduroam