The Only Option I found for you:

1. Work full time in summer.

2. Like Guest4 said: Talk with your employer and set up the work 40hrs/week and tell them to pay you for 20 hrs but to bill you at double rate.(It does not matter even you work 50 hours just make sure the billing rate is higher). If it is possible.

Last Option,

The Job market is tough nowadays, I suggest even the rate does not goes above, work 40 hrs and get paid for 20 hours for 4 month. It will not be so bad for future...

Nepali Thita