The DAAD, German Academic Exchange Service, provides financial support for the organization of Summer Schools in Germany via its Summer Academy Program: https://www.daad.de/hochschulen/programme-weltweit/sommerschulen/deutschland/de/23467-sommerschulen-in-deutschland/
The DAAD is also able provide financial support for Summer Schools held abroad: https://www.daad.de/hochschulen/programme-weltweit/sommerschulen/ausland/de/23469-sommerschulen-im-ausland/
ERASMUS Intensive Programs (IP) are compact, structured study programs involving universities in at least three different countries participating in the ERASMUS program. At least one of the universities must be in an EU member state. Study credits must be accordant with a credit point system, e.g. ECTS, recognized by all the participating universities. To qualify as an Intensive Program, the projects, i.e. summer schools or university block seminars, must have a duration of at least 10 consecutive work days (interruptions are only allowed for weekends) and not more than 6 weeks.
ERASMUS Intensive Programs offer students and instructional staff possibilities to explore interdisciplinary topics in multinational groups. These should be topics not usually dealt with, or only infrequently taught at universities. Funding will only be made available for particularly innovative projects involving an interdisciplinary approach and, moreover, exhibiting significant added value within the European context.