Temps in the 40s won't do anything bad to your tomatoes. You're looking out for freezes, not chilly weather. The tomatoes won't grow much when it's cold, but they'll survive fine. You'd like soil temps to be in the 50s, though, and your soil is easily that.

If you want to play odds about freezes, get out your zip code and go here.

http://davesgarden.com/guides/freeze-frost-dates/

Normally I'd say sure IF that forecast was the only issue. But it isn't. The US is in a very weird gulf stream/jet steam weather pattern right now and the series of storms that nailed North Texas, OK, and us the past 2 days with 9+ inches of rain, hail, floods, tornadoes and 60+ mph winds is now headed straight toward your neck of the woods. Unless it breaks up substantially over the Appalachians you are going to get hit with at least part of it.

I was lucky that the soil hadn't dried out enough last week to plant as I normally would or I'd be dealing with a real mess today.

Dave

the problem here in Northeast is that it's cloudy as heck for the last few weeks.. rain is about average, but out of the past 2 weeks only around 2 days of those were sunny. the cloudy pattern seems to continue in the extended forecast.

your temps are about the same as mine (i am in CT) and my plants have been in the ground since April 10th.

The temps look acceptable but, as Dave says, you wouldn't want your plants out in bad weather. Even here in the north the winds are fierce!

I would hang on......

Linda

I've read that temps below 50 can actually permanently damage tomatoes.

My soil is quite warm, BTW. Three inches down its near 70, thanks to being fluffy and newly cultivated.

i must be growing special tomatoes then ;)
i don't know where you read that. they will grow even at 50 degrees, slightly slower, but they will not be harmed at all. if the plants have already been harden off, they can survive down to 40 with no problem. you wouldn't want to keep them at those temps for long,as in days, but a day or two won't cause harm.

I've seen that too, where some people claim that tomatoes will be "stunted" by low air temperatures. Never ever seen that, and I've had a lot of tomatoes that were sitting happily in 40-ish temperatures - even down to almost freezing. I'd venture that's yet another gardening myth. Myths die hard. But as has been pointed out here, low soil temperatures can be an issue.

As it turns out, I never get soil temps below 50F, partly because of my climate, and partly because I dig in uncomposted material early in the season that, as it composts, contributes heat to the bed.

I got my first batch in the ground here in E. Tn. about a week ago after we got hit with tons of rain. I had the 2 beds covered, and as soon as the rain passed, I put them in. We'll get hit with the rain that Dave mentions tomorrow morning, but it's breaking up a bit and should be fine. There's a few colder days scheduled next week, and I'm watching to see when the next batch will go in.

In my experience, while there's something to be said about getting an early start, plants tend to thrive much better when they can 'hit the ground running' with nothing to slow them down. You'll notice that plants which have to deal with adversity fair little better than plants that were sown, or transplanted weeks later under ideal circumstances. However, there's also other issues of space, lighting, transplanting to larger containers, etc... that can sometimes make putting them out sooner rather than later a good choice. Each circumstance is different. Few are distinctly 'better'... unless we just make an error in judgement and should have done something different.

Anyway... sometimes 'rolling the dice' hits the jackpot. Other times... we're glad we held off.

Other than frost/freeze, nothing serious can happen to tomato plants . I have seen peppers stunted but never tomatoes. The only thing is that they might grow very slowly. If the soil temperature is around 50F (or higher) they will actually grow in cool air temperatures. Back in PNW I always planted early April that followed lows down to 36,37F on occasions. The night lows didn't get to 50F until July some time. And I managed to get some ripe tomatoes around mid July.

Sey

Although lows still don't look bad, today's forecast now says we stay in the 50s for a high Saturday...

Well as everyone has posted, forecast temps aren't really a concern. It will be much warmer closer to the ground anyway than any forecast temp. So whether you plant them now or not, if they are fully hardened off, is your choice.

Dave

40 degree temps might cause blossoms to drop if the plants were to that point, but without an all out freeze it should be no problem at all. I'm a couple hours south of the OP, and I have at least half my plants in with at least a week worth of nights down in the mid to low 40's in the extended forecast. Not really worried about that.

Temps forecast have trended down some.

However, I'm going to plant them, maybe with row cover on them for a week or two.

10 miles south of D.C. I planted my tomatoes in ground 3 weeks ago. Temp changes into the 50s and 40s at night have been experienced. I have flowering on some cherry types. The real danger is low soil temps which would result after prolonged cold. I've had in ground tomatoes in 40 degree weather. If you do a row cover, I'd be sure to lift up the sides during the day to allow air flow. You will cook those guys if we have a hot sunny day.

I'm planting them tonight.

However, with the chilly forecast, I'm worried the soil temps will start to drop as well.

I don't think you will see damage. If anything a slight growth stump until warm up, but the root establishment in their final location is worth it. Plant them really deep.

Soil temps don't fluctuate like air temps do. It takes several days to see even a couple of degrees drop in soil temps due to air temps. A heavy cold rain can drop them quickly but even then only marginally, but not air temps.

If you use row covers do not leave them on during the day.

Dave

Are you SURE I should plant them?

https://www.washingtonpost.com/news/capital-weather-gang/wp/2017/05/02/big-chill-to-invade-eastern-u-s-this-weekend-and-may-get-stuck/?utm_term=.57b58ec0f3f4

what is your exact zip code?

21029

I have no fear of lows in the 40's and even high 30's. It will reach that temperature for just a few hours before sunrise and heat up to tolerable levels once the sun comes out. The temps won't be low enough for long enough to really sink the soil temp too low. I'd get your plants in ASAP so they recover that initial shock, or just wait until after the cold passes.

My location has the lowest low in the next 10 days of 45 and that doesn't scare me at all. I'm still pinching all flowers to promote bigger initial growth.

I'll do it now. It will be as much of an investment of time to try to keep them going in containers as it would be just to plant them.

Looks like you have about 4 days in a row with lows in the 40's. Why not just wait until next Thursday. If your plants can wait, just wait. If I was you, my plants would have been in the ground 2 weeks ago. I think they will do just fine if you decide to plant. But do so soon, so they can get over the initial planting shock.

The link I posted suggests it could actually be after Mother's Day before it warms up that much.

When I plant, I really notice a burst of growth in just a day or two. If they are leggy, plant them deep. I try and plant them deep up to the first set of branches, and usually just pinch off those branches. Mulch them if you can, with grass clippings or leaves. This will help insulate from the cold.

I'm not worried about a loss of plants, just stalls them if colder. No big deal. I think it is still better to have them building their root base as the soil will be warm. By this time of year I'm sick and tired of watering indoor plant starts. I plant out as soon as possible. Heck these days I'm so lazy my orchids go out at lows approaching 50 degrees.

Do what you feel comfortable doing. Personally, I wouldn't be concerned about those temperatures for tomatoes and would rather see plants in the ground in those temps than continuing to struggle along for another week rootbound and sickly in containers. But they're your plants. If you feel that fearful about it, arguing with people on the Internet who will just keep telling you the same thing--that lows in the 40s aren't concerning, especially after soil has warmed--isn't productive. It's YOUR decision.

If really worried just do the row cover. The important thing is make sure there is a tight seal at the bottom to keep in hot air which the ground releases. If you have a large volume of space over the plants, you could probably get away with leaving it on the plants during the day. Your highs look like they are only going to be in the 50s-60s. But monitor the heat level as you can fry the plants. I grew lettuce under row cover all winter. It never died from the cold. When we had days in the 70s I opened up the ends of the tunnel to allow air flow.

It's the length of the cool snap that worries me. Soil may start cooling down at that point.

I am going to plant them. Either tonight or tomorrow (I get home from work pretty late on weekdays, so time can be an issue.)

I'm planting tonight. Despite the "f" word creeping up in one local forecaster's write up. Scattered frost mostly north of the PA line (York, Lancaster) per a couple models.

Almost all forecasts I see for me still say lower 40s...