April 3rd I could check the activity.

Female Thamnophis radix appears at 10 AM on April 3rd.

It had not frozen anymore the past night and around 10 AM I saw the T.radix female crawl out of the hibernation bunker. It was only 3°C and there was a little bit of sun (not very intense). Finally the 1st signs that spring was coming. She was the only snake to come out that day.
But of course it was still very cold!

April 6th temperatures were a bit better and the sun was stronger.

T.radix couple and T.s.pickeringii male basking at 11 AM on April 6th.

At 11 AM the T.radix couple and the the old T.s.pickeringii male were basking on the best spot in the terrarium.

These 3 snakes continued basking until the sun left the terrarium around 1 – 2 PM.

Max temperatures around 10 °C.

T.radix couple and T.s.pickeringii male basking at 11 AM on April 6th.