I'm a bit north of you in the Lehigh Valley. There is a guy that gardens just south of Allentown, he also considers himself zone 6.

this is from his website which I have linked below

"The weather
Our area is squarely in USDA zone 6, meaning winter temperatures don't typically drop below -10°F (-23°C). Philadelphia is a zone warmer, the Poconos a zone colder. And of course winter temperatures vary quite a bit from year to year - for several years recently, temperatures never dropped below 0°F, but last winter was characteristic of zone 6. We cannot count on a consistent snow cover to insulate the soil from the harshest temperatures, so marginally hardy plants are best mulched with a few inches of organic material.

Typical last frost dates are around early May (so the freeze on May 21, 2003 caught us quite by surprise), and the first frost in fall occurs anywhere between mid-September and mid-October. That leaves enough of a gardening season to grow almost any vegetable, although heat-loving crops such as tomatoes, eggplants and peppers need an indoor headstart to start producing by mid-summer.

Summers have been variable as well: in our eleven years in this garden, we have suffered through two disheartening years of drought, and two unusually wet summers. For the most part, though, we can count on some stretches of the warm season where supplemental water is needed to keep garden plants alive and happy. Every summer brings plenty of hot and sticky days when gardening isn't particularly pleasant, but many plants that can't survive the humidity of the Southeast do OK here."

Here is a link that might be useful: Rob's Plants

I don't know if what I have to say will help, but you might be confusing "average last frost date" with the date where you are pretty guaranteed not to have frost. Average last frost date means you have a 50% chance of frost after that date. Make sense? Mother's Day or thereabouts is usually what we use as the date when it is entirely safe to plant out tender annuals.

Same here re Mother's Day. I generally assume we'll have at least one frost on or about that time with the occasional freak event nearer the beginning of June.
One of the (many) nice things about WS is you can plant out and save the top half of milk jugs to use as cloches to cover tender seedlings that have been planted out if there's a risk of frost. I've heard Token & others mention using those. I guess you could also plant out just a few of the seedlings, hope for the best, and keep some back for a worst case scenario.
I also tried getting a more accurate last frost date but the USDA only tracks Hartford, CT & Boston, MA--nothing in between and I'm halfway between the two. That's 150 miles of ??? What do I do? Split the difference between them? It's not that easy since microclimates factor in--elevation above sea level, hills and valleys, open space vs. forested land.
Since I've never grown broccoli, I can't offer any advice in that regard but will be interested to see what others have to say.
Best of luck!

I'm worried about that now that I had to uncover over 375 things. If there's a frost, I'd be scrambling to save the seedlings. My son said he would help me if it comes to that.

It's very warm here, but we're nowhere near last frost, even if I gambled on a percent chance.

go to this website - it's the National Climate Data Center which allow you to pick by state, and for PA, has at least 50 town.

Shows last frost, first frost and breaks down probability by 90%, 50% and 10%, by 36 degrees, 32 degrees and 28 degrees.

i think it's the cat's meow!

Linda

Here is a link that might be useful: National Climate Data Center

Thanks all. Linda, I've used that site, but the closest place on the list is probably 20 minutes away.

Last weekend, when all the forecasts called for below freezing temps in the region, the local monitor on weather underground showed we never went below 33, so microclimates count, too. I'll still wait for mother's day for tomatoes and such, but I think the broccoli can go in about now anyway.

Craftlady, I started my eggplant by WS and i've got some nice sprouts already

Just to throw another wrench in the works, I have heard that you can get frost if the temps dip down to 36. Even though 32 is freezing. Odd, but I swear I've seen it happen, too. (And it makes sense for why they have that 36 degree map.)

Your county agricultural extension office might be able to help some with microclimates in the county. Also, for what it's worth, frost tends to accumulate in low areas, so if your property is at the top of a rise (like mine) you may not get frost even when the folks at the bottom of the slope do. If you're at the bottom of a valley, you will be more likely to get frost. Here in east TN - zone 6b/7a (depending which map you look at), I don't put out tender annuals before May 1, either, unless the weather forecast for the week at the end of April shows absolutely no chance of frost.

That kind of goes with what I was told about the wind keeping frost away because frost is the moisture settling. And I am at the top of a hill.

Vvesper, it's funny you mentioned that you're 6b or 7 depending on the map because we are, too. If I went by i-village's zipcode id we're 7, but another said 6B.

Caryl

Generally speaking, the weather here is more like zone 7 as to minimum temps. But every so often, we have a really cold winter. I don't care as much with perennials, but I try to make sure shrubs and trees are fully hardy through zone 6 or even zone 5, just for insurance.

The record low here (in 1985) was -24 degrees. Yes, farenheit! Some zone 6 or 7, huh? Most years we don't get below 0, though we very often get down to single digits for a night or two here and there. This year, it hovered in the 20's for over a month, I think - which seemed harder on borderline plants than the occasioanl dip for a few hours.

Usually broccoli is planted as a transplant with seedings, instead of direct seeding. It can be planted fairly early, 4-6 weeks before the last frost date, as it can take a light frost with no problems. From: How to Garden Guide.

I have had my broccoli out for the past 3 weeks. I did have it under plastic the first week. You can also use buckets, cardboard boxes and such if very low temps are expected. Also planted out cabbage and some Romaine lettuce. Temps have dipped down to the upper twenties,so I covered. Temps of 30's they went unprotected. I'm in zone 6, southeastern CT.

Donna Mae

Here is a link that might be useful: How to Garden Guide