I do not want to discourage you, but I do not see a chance for your water melons. Water melons probably would need atleast two months of warm weather after the fruits are set. You could have started your seeds inside and transplanted them after last frost. Then you may have had a chance.
I cannot imagine growing melons, watermelons, pumpkins in zone 3. But you can grow the best cool crops.

thankyou for the heads up and at least it confirms my suspicions thats too bad but it was fun trying to see how far they would go .I do have pumpkins though and they are doing just fine 3 healthy ones now and 5 more just days away from flowering . I did pumpkins last year and they do well here .

I'm in zone 5(though some say we are now 6) and I have given up on my melons this year, some are getting quite large, but with the cool summer I just don't see them having enough time. If yours are only the size of peas, sorry to say, but no way. Maybe we'll have better luck next year!

yes i'd be thinking from seedling stage as far as i know you need about 3 months of longish hot days, maybe next year pregerminate the seeds into a planter tray or planter tubs so they are well developed as soon as you are able to plant them out.

you may need to introduce some bottom heat to get the seeds to germinate?

len

Here is a link that might be useful: lens garden page

In Zone 3, I would use all of the tricks known to grow a crop like watermelons -- set out the largest transplants you can, use black plastic to warm the soil, and a hoophouse or tunnel structure to warm the air.

It was just a plain bad year for water mellons up north my biggest one is a little bigger than a softball I pretty much gave up on them in june they were stunted by a cool spring and never got going on the other hand I have ripe pie pumkins and others growing like crazy
{{gwi:98379}}

I have one melon - it's somewhere between softball and volleyball size and I think that's as good as it's going to get. The vine is dying. Figures - just as it finally starts to get really warm. Oh, well, we gardeners are nothing if not optimistic -- there's always Next Year!!
Cheers,
Edie

Reading this thread makes me all the more upset with our puppy who pulled out two of our three watermelon vines (among many other garden growth). Each vine she pulled out at the end of June had two or three softball sized watermelons!! ediej1209, we have one vine left with one melon similar in size to yours chugging away. Reading this I'm feeling lucky to have that at least! None of the books I've ever read has listed puppies as a garden pest but she's the worst we've encountered yet! :)

I have so many watermelons and casaba melons that I am starting to get sick of them. It is too late for your zone. You can try some of the stuff that the other posters recommended but it's too late.

Here is a link that might be useful: Win a 50.00 Home Depot Gift Card

Can't hurt to put some plastic hoops over them. Or if that's too inconvenient, a frost blanket or two (at night). They may still die from chilling injury but if we get a warm September following a frost, they may grow a bit more.

Unfortunately, the meteorological models seem to suggest that the Canadian Prairies (is that where you are?) will finally warm to above normal in *November*.