Heat wave isn't +30°C. This is what climate change deniers want people to think.
A heat wave is when the temperature are higher on a certain amount of time. According to the IPCC, it's "a period of abnormally hot weather, often defined with reference to a relative temperature threshold, lasting from two days to months", and according to the Heat Wave Duration, and to the World Meteorological Organization, it's "five or more consecutive days during which the daily maximum temperature surpasses the average maximum temperature by 5 °C (9 °F) or more".
I didn't do a ton of research but that seems pretty warm for October. I'd expect the average to be way lower (12° for the red dots maybe) with an occasional warm day or two.
I like this site for checking the climate in specific regions. This shows 13° as the average day-time temperature in october. If the DWD forecast is to be believed Lübeck might get up to 18-20° in the coming one and a half weeks. So while it's not the mid 20s it's still way above average.
On the other hand, for sure make the best of it and keep the grill out. Looks like fantastic weather for it!
Talk for yourself. The last week and the coming week here in Switzerland are exactly what the article is describing. Around half the days were 24°+ and even the lower days are around 17-18°. That's definitely not usual for late September and early October.