Remember....I write mostly for the benefit of Americans and non-Germans....so if you are German and don't see the need to listen to this for the 100th time.....just look away or day-dream about magic unicorns.
German states (all sixteen) run their own vacation period scheme for each summer.
For example.....last Friday (25th), was the last day of school in Hessen and Rhineland Pfalz. These two states then started a six-week period of off-time for schools.
What develops by Friday afternoon is this chaotic run by parents and kids.....loaded with bags....and piled into a van for the airport or in the family car bound for some cabin or resort in Germany or a nearby country. If you were around the autobahns on Friday afternoon.....you kinda noticed a big swing up on traffic....especially near Frankfurt and it's airport.
The airlines realize that Friday, Saturday and Sunday (26th, 27th, and 28th).....are a chaotic period where people are desperately trying to get out and start their vacation.
At the end of the six-week period....the same will be true on Sunday.....as people try to come back home that afternoon or evening.
If you are a company in the Hessen region....you have to be fairly open to the idea of your employees demanding their two or three weeks off....during that period. That means that you might be running an operation in July or August with only fifty-percent of the crew in the office.
If you walk into a government office for help.....you might find that of the five people in the office....two are on leave and one is on some last-minute sick-leave episode.....and the two remaining people don't know much about such-and-such forms.....so you got to come back in two weeks to get some paperwork done.
The latest state summer schedule? Bavaria traditionally comes up last. Their period will start 1 August and not end until 14 September. The earliest is North Rhine Westfalia with 29 June of a start date.
An affect on autobahn travel? Yes, to the extreme. If you'd started your vacation a week or two before any of the states....you'd probably come to say that traffic was thirty to fifty percent less....especially on a Saturday or Sunday.
On several occasions, I had the pleasure of driving on a Saturday from Frankfurt to Denmark during the summer break periods. The first time....I came to be fairly stressed out by noon as the traffic had slowed down because of accidents along the way. The second time....I got wise and was able to convince the wife to get up at 3AM and get a headstart over the typical German driver. That gave me roughly six good hours of open roads before the 'cluster' started up.
What you tend to notice after a while is that older couples without kids.....will start their vacation periods in April or May....or toward October.
So when a German brings up the summer vacation planning process and it has to fit within a schedule.....you can easily grasp why people are thinking about this already in March or April.