Low Temperatures

I just need a opinion from anyone who can answer. I live south of Chicago. The temp is supposed to drop to 40 tonight. I have 54 plants in the ground and no way to cover them. Will a temp that low hurt them? They have been in the ground for a while now almost two weeks.

Tomatoes? Peppers? My tomatoes have been in the ground in under 40 degree weather, two cloudbuster storms, and two times of small hail and they look fine. Peppers are a little more delicate and I hadn't put them in the ground until last week. In years past they too have gone through a bit of weather and survived.

I went out this afternoon and put back plastic pots over my peppers and such.

Thanks for the quick reply. I did go out and cover the smaller plants. I just did not have enough pots to cover everything. But now that I think about it mine have survived a little stormy weather to.

It seems like the minute I set some plants out or plant some seeds, they go and change the forecast.

I watch Accuweather for my zip code. I never plant tender things out until the nighttime temperatures are consistently over forty degrees for at least a week or two. I have planted out things that can take a light frost like broccoli, spinach, brussel sprouts, cabbage, onions and even my wave petunias and verbeneas and marigolds. Things like tomatoes, peppers, squash etc. need heat and won't grow any faster if you put them out a few weeks early. They will just sit there in the cold soil and shiver. In fact, they will sometimes suffer shock and take longer to recover when it does warm up over those plants left in their pots in a garage. I won't sow beans or other seeds until the soil has warmed up to fifty degrees for good germination. For my area it is usually safe to plant on Memorial weekend but every year is different so you just have to monitor the nighttime temperatures. Last night it got down to 36 degrees where I live. Usually, it is not that cold at night by mid May. I'll just keep an eye on the weather and wait. I'd hate to lose any of my plants or stunt their growth by planting too soon.

As long as the plants have already been well hardened-off, then 40 overnight is fine. It's mid-30's that's scary.

I always check Weather Underground and NOAA since they seem especially pessimistic and usually lowball overnight temperature predictions. Although even they are not *always* right. They've predicted 36 and we've seen 32.

Never trust the weather man on TV or even some of the weather websites out there which are very optimistic and not 'serious' about nailing an accurate overnight temp. What drives me crazy is weather forecasts that give a high and a low and these numbers don't seem to have any basis in reality. Like the high is the temp at 2pm and the temp at midnight, or at 6am, neither of which is necessarily the hottest or coldest part of the day. Truthfully I have been able to figure out how some newscasters determine their High and Low temps but they are certainly NOT the highest and lowest temperature I've seen on various days.

This message was edited May 20, 2008 9:31 AM

I track Accuweather's 15-day outlook for my zipcode, but the forecast keeps shifting.

Last week, it was looking like Thursday might be the day to plant the most tender things - now it's predicting another 40 for that night, and pushing the planting day back to Saturday.

I've tried early plantings of corn twice already this year, but I'll probably have to go for a third.

Writing from a totally different perspective--zone 2a--where corn and beans are but a distant dream! But in my unheated greenhouse, where I keep a min-max thermometer, my tomatoes and squashes often drop to below 40. They don't set fruit at those temperatures, but it doesn't hurt the plants. Peppers are a bit touchier, but they'll survive too.

Outside, where we still get temps down to 25, I've already set out my brassica, root veggies and greens starts, plus seeded a few others. I now have agricultural fleece to throw over them at night (it keeps the frost off and also protects tomatoes down to 28, so I've read) but years ago I found that any covering at all worked--sheets, light blankets, plastic.

There are no weather stations anywhere near where we live. We take the readings from one located closer to the coast, and one located a hundred miles in the other direction, and then look out the window. If it's in the 30's at 10 pm and clear, we're sure to get frost. If it's cloudy and high 30's, probably not. The other morning I awoke at 3:30 am and realized I'd misjudged--and went outside with my gumboots, dressing gown and headlamp to cover things!

I imagine it's more difficult where you simply never expect to get frost at this time of year! Good luck, and keep those sheets handy.

You probably don't want to spring the $150 for it, but I'll just say that Weather Underground encourages people to buy their own weather stations and then will add that station to their network.

If it's any consolation, I would love to be able to grow Brussels sprouts and parsnips as easily as you can.

And lettuce all season long!