i'm not super far north, about 43 degrees north, about level with rochester ny.
in the 5 or so years i've been growing peppers, frost warnings happened end of september once, but all other years have been mid-late october.
last year i started the pubes in mid-feb, and from 5 plants got approx. 50 ripe peppers, another 50 semi-ripe which did colour up more when left in a box for 1-2 weeks, and another 50 unripe.
this year i started them on january 1st. they are definitely way farther along, but they maxed out the 3" pots which may have stunted their further growth now that they are in beds outside. still going very well, and some pods are already forming.
next year i will aim to start around jan 18th, and/or be more prepared for second indoor up-pottings.