Your spinach is likely going to seed with this hot weather last week.  You can remove the plants, then plant more spinach or another crop as there is lots of growing time left.

Saving Spinach Seed:  Let one or two plants go to seed.  These plants are unusual in that the seeds are produced up the whole stem.  Remove them once dry.  NOTE: Don’t save seed from the first plant to bolt or go to seed or your seeds will also have the tendency to bolt early.

Cool Customer: Did you know that spinach won’t germinate if the soil is too warm?  Don’t waste time planting seeds in mid summer, the seeds won’t grow.  If you want more spinach, start the seeds inside or in a cool area then transplant the seeds to the garden once they start to grow.