Going by temperature, not the calendar

When I neared the pool below the sewage lagoon this morning, I heard a scurrying in the reeds that bordered the pool.  It was a good-sized painted turtle, that quickly sank into the water.  I saw two more basking in the sun's warmth at the pool's edge, then this one at another spot.  I suppose I shouldn't have been surprised that the warm temperatures brought them out of their winter's bed, but a whole month early??  Last year's first sighting was April 23rd.