Warning: I've never grown pumpkins! If anyone with experience answers, believe them, not me!
On the other hand, this rambling answer shows the factors, so you can know for yourself "why", and apply the same reasoning to any other crop in any other climate.
I see "100-115 days to maturity" in some seed catalogs. Call it three and a half months.
< < Edited to say: it's been pointed out that I counted wrong, there are NOT 100+ days remaining between now and Halloween. Also, apparently most people direct-sow pumpkins, not transplant them. > >
I think that seed catalogs list "DTM" for favorable growing circumstances, which I think are "warm to hot, very fertile soil, plenty of water, but well-drained soil and/or hills". Full sun and LOTS of room.
If your weather for the rest of the year and soil are good for pumpkins, you don't have to add 20% or more to that number to guess how long they will take in your garden.
If true, they would be ripe around mid-November.
However, "DTM" for plants that are usually transplanted usually count from the date of planting out. I assume you meant "start from seed".
So add around three weeks for the seedlings to grow, then another week to harden them off before planting into full sun and wind.
Now we're thinking "maybe ripe around mid-October".
Halloween isn't until October 31, so I would guess that you have a good chance, IF your actual future weather and soil don't make your seedlings grumpy and sullen. Like, too cold for them, or too dry. Less than full sun. Insect damage. Plant diseases. (At least poor pollination doesn't slow them down, it just means fewer pumpkins.)
Maybe you can harvest pumpkins for decoration weeks before they are fully ripe, or as big as they might ever get.
Depending on where you live, cold might set in before they get big enough to use, and that could slow their growth down.
If you say where you live, someone here can probably just say "yes, no or with-good-luck".
If I knew what temperatures pumpkins need for rapid growth, I would ask when your average weather gets much colder than that. Then you could guess whether "100-115 days to maturity" is going to be accurate for you.
Maybe people epxerienced with pumpkins could answer just based on your average first frost date.
I don't think your USDA Hardiness zone is useful for figuring "last seed-start-date" or "last transplant-out-date". That just says HOW cold it gets in an average winter, not how SOON it gets too cold for pumpkins to be happy and healthy.
P.S. If you
- click on the "head and shoulders icon" in the upper-left corner,
- then "Change your public profile",
- then edit "location" and "Extra one-line info",
these tidbits of info will appear on all your posts and help people answer questions.