\"As soon as soil is workable\" ??

     The instructions for planting pea or spinach seeds say "plant as soon as the soil is workable" but I've misjudged that in the past. Germination temps are listed as 40-80°F and even though it is a balmy 50° outside now, the 10-day forecasts predict several nights around freezing coming up. Yes, it's almost April and I can "work the soil", but my instincts say wait. What do you pea and spinach mavens recommend?

I sow English peas, spinach, beets etc any time the ground has thawed to a depth of 4-6 inches and is sufficiently dry enough to work.