One of my broccoli plants is about to flower. Googling has revealed that I
should nip the flowers if I want to have a chance of harvesting some
broccoli. There is only one bud which is not even golf ball size! What
would cause it to flower so early in the season? I'm in the North East
where it has been cool and rainy for the early part of the summer. Now it
is mid-80s and mostly sunny. Is that why?

Could be any number of reasons why Broccoli will "button" i.e. form tiny flower
heads, Primary reason is usually the the plant was stunted somewhere alon it
growth cycle, I have seen plants kept in theier trays too long and actually
button before transplanting. Sometimes a cold snap will cause the same
phenomena in the garden, Cabbage root maggots and root diseases will also cause
this, If your plants are growing well, then harvest the button and hope for
more normal side shoots. Once the flowers open up the plant will divert all its
energy to producing seeds,