Apr 26 is considered the long-term avg date of last freeze (32F) for Hartford. Means there a 50% chance of a freezing event after that date. The link below includes 10%, 50%, and 90% probabilities for stations in CT and all other states for spring and fall frosts and freezes. If you want the most conservative date then go with the 10% date, and that's May 6 for Hartford. Of course the actual date for any one year can differ from these averages quite a bit, but they are good starting point. And there are local microclimates, so alot of backyards near that weather station may experience differences. Here is a link that might be useful: NCDC frost/freeze data

Hate to break this to you, Kawaiineko gardener, while there is a technical last and first frost date for Boyne City and the rest of northern Michigan, these are just averages, and ... well, as we all know, there are always outliers. Frost can and does happen every month in your part of Michigan. My uncle lives about an hour south of you near Cadillac, in a place called Tustin, and my sister lives just outside of Manistee. Both of them have had hard freezes in mid to late June and again in early September, and both have reported frost even in July and August, albeit light ones that didn't really hurt anything. It happens. Last year was especially challenging up there, with late, hard freezes in May and hard frosts in June. My uncle lost his garden twice to frosts, first around Memorial Day, and then again about 3 weeks later after he had replanted. Both of them said it was really hard to find transplants at the local greenhouses because everyone got wiped out and had to do it all over again at least one time, some people twice. The year that my sister moved up there for good, 1993, they also had 4 inches of snow on August 28th, although it melted away by 10:00 the next morning. We had it really cold, wet, and windy the same day, with a high around 48 and a low around 42, but no snowflakes, thank goodness. And, it turned around and got up to like 93 the next week. Michigan weather is just plain WIERD. I hope this year will be better. Even down here near Detroit it was COLD, COLD, COLD all summer. July had several nights where the thermometer in my backyard hovered around 38 degrees, just above the point frost could begin to form.

I would contend that the term "Last Frost Date" really means the last front date - as in no frost after that point. That aside though, your real question is about the directions on the packet. Making the assumption you're talking about something you would start inside to avoid frost, the date is simply a guideline of how soon to start them before you put them out (regardless of when that is). The hazards of starting seeds inside are that if you start to early, your plant is big enough that it needs to go outside before it's safe for it to go out (due to the frost). If it stays inside to long then you have issues like becoming root bound because the pot is to small, not getting enough light because the small little grow light you started with just isn't going to cut it anymore, or even that the plant is ready to start setting fruit and your inside environment isn't prepared to give the plant what it needs to do that. The other hazard is that you start to late in which case the fruit from the plant doesn't have a chance to reach maturity before your first fall frost sets in - so make sure the growing season is long enough for whatever your planting.

Renee - LOL! Amen to that. As of April 11, we have a 50% chance of frost. By April 26, that drops to 10%. Last year, we had a cool night around May 17, but no frost. This year, we haven't had a frost since March 9. We've been near freezing several times, but no frost. In the fall, we usually get a late October or early November frost. Had a very light one this year in November. The killing frost came on December 5. You can find the numbers for your zone here. NCDC. Choose your state, then find your town on the pdf file that pops up.