When Is The Right Time To Dig?

I really don't know. I know it's not today and probably not tomorrow after trying this morning. The very top is dry but the underneath is too wet. As I put my foot down and felt the resistance the fork was giving I knew if I carried on the fork would  break. I pulled it out and the marks told me no don't do it. 

So when exactly is the right time? I'll be blowed if I know but I hope that time comes soon. If it doesn't then I'm back to covering the weeds on the undug areas. Sigh....and so the adventure continues.