After having 34°C (93°F) five days ago, today in the morning it had -2°C (27°F).
It's called the "Ice Saints":
It snowed down to about 1000 meters, which is about 200m above where I live.
This is a picture I made today from my house, looking up to a snowed in mountain:
Frankfurt tradition is also Pancrace-Servace-Boniface-Sophie.
The coolish days in mid-june are known in German as the "Schafskälte" (sheep cold) because they come up right after shearing. Sheep lose their wool naturally after mid-june.
As to your temperature differences... well there are now
four official, state weather stations in Frankfurt... they've opened a new one... and their respective daily highs for today are 29.4° (East), 29.0° (Höchst), 28.5° (Lerchesberg) and 27.5° (Sindlingen)... and Sindlingen is next door to Höchst.