So will peppers survive 40 degrees? To sum it up, most peppers won't necessarily DIE from 40˚ F temperatures, but their growth can be stunted, and they may be slow to recover so it's best to keep them warm if possible.
40F won't hurt any of those plants but if the soil gets too cold they can all be affected. So if it's me I cover if I think the soil might get too cold too long. Most warm season crops I like to maintain 60F soil temp minimum.
Temperatures below 60°F at night will also result in blossom drop. At temperatures below 40°F, peppers may show some chilling injury. A shortage of water at bloom time can also result in blossom drop or failure to set fruit.
Each plant has a different threshold when it comes to dealing with the cold. Some plants can survive outside even when temperatures hit freezing. Others need to be brought indoors when temperatures reach the mid-40s.
Cucumbers are heat-sensitive and do best in temperatures between 60-90°F (16-32°C). They can tolerate some heat but will become stressed if temperatures exceed 95°F (35°C). Cucumbers can also be damaged by frost and temperatures below 50°F (10°C).
So when temperatures start dipping below 50º F, leave the tomatoes on the vine if warmer days and nights are forecast. But if temperatures have started on a steady downward slide, go ahead and pick the mature green tomatoes and bring them indoors.
H2 Rating - 34 to 41° F (1 to 5 C)
Overall, these annuals are the most delicate of all the hardy annuals - one might call them half-hardy since they are really only hardy into the few temperatures just above freezing. And it's important to NOT let them freeze.
Zucchini is a warm-season crop that cannot tolerate frost or freezing temperatures, so its best to plant your zucchini in the early summer, when temperatures are at least 70 degrees Fahrenheit or more.
If you're trying to squeeze a few more days/weeks out of your pepper harvest and the temperatures are dropping at or below 40˚ F, we recommend covering your peppers with frost cloth or a small hoop house with greenhouse film to keep them warm during the cold nights if you can to help them keep producing.
Plan to bring in your houseplants when temperatures are forecast below 45 degrees F to protect them from stress and cold damage. Tender perennial herbs like Rosemary or Lemon Verbena can be brought indoors as well for winter cooking.
Know Temps for Fruit All Summer
Another temperature to keep in mind: tomato plants will not survive in temperatures below 35 degrees Fahrenheit, and will not thrive at temperatures below 50 degrees.
Crops that came from warmer parts of the world cannot tolerate even a light frost, and may even begin to suffer at temperatures below 50 degrees Fahrenheit. Basil is an extreme example of this, as the leaves can turn black when the temperatures dip into the 40s.
Hold back on planting for two weeks after the risk of frost. After planting, protect your plants (pepper plants in particular) from the wind and cold by wrapping a sheet of clear plastic around several plants in such a way as to create a fence, or wrap a single tomato cage (one plant) at a time in clear plastic.
A local study done on frost formation relating temperature to dew point has these guidelines for frost: temperatures from 38 to 42 F can lead to patchy frost, 33 to 37 areas of frost, and 32 and below widespread frost/freeze.
Cover Plants
Once temperatures drop below about 28°F, covering is typically no longer effective at preventing cold damage. Occasionally even with covering you may still see damage at temperatures above 28°F, especially when the below freezing temperatures are prolonged (5 hours or more).
Climate. Transplant outdoors after nighttime low temperatures are above 50°F. Dry soil, temperatures above 90°F, or night temperatures below 60°F or above 70°F, can weaken plant growth.
First, it's good to know which plants are sensitive to temps around 35 or 40 degrees F. These are common tender plants that will need some protection. Hanging baskets: begonias, calibrachoa, gerbera, impatiens, vinca, euphorbia, and scoparia.
Daytime temperatures below 65°F can lead to fruit set failure—the pepper equivalent of stage fright. At night, anything under 50°F is an invitation to leaf curl and overall plant stress. It's like the plants are pulling their leaves up to their chins, trying to keep warm.
The morning sun is favorable because it is less intense than the afternoon sun. If your plant receives at least 6-12 hours of sunlight, it will have more energy to grow tall and strong. If your plant only receives 6 hours or less of sunlight, it will likely have a smaller harvest.
Even prolonged exposure to temperatures below 55 degrees F. (13 C.) can cause decay, pitting, and water-soaked areas on fruit. Sudden cold snaps can cause cucumber plant damage on leaves, stems, and fruit or even kill the plants.
When do I know it's safe to bring my plant outside? It's safe to move your plants outside when the outdoor temperatures stay consistently above 50°F. Pay attention to the weather report. If nighttime temperatures are set to fall below 50°F, bring your plants in for the night.
After that, the daytime temperature should be maintained at a minimum of 18°C, and the nighttime temperature at a minimum of 16°C (60°F) to ensure that enough male flowers are produced for adequate pollination. In the summer, daytime temperatures can get up to 23° to 25°C (73° to 77°F), which the crop can tolerate.
Seedlings, with their tender new leaves, often give up the ghost when temperatures dip to 32-33°F. Tropical plants have differing low-temperature thresholds. Some keel over when temps fall to 40°F; others crumble at 35°F. Other plants are just hardy by nature and can withstand temperatures as low as 18-20°F.
Many newer cultivars are able to withstand hotter temperatures, but no petunias thrive in chilly temperatures. When spring temperatures dip below 40 degrees F, either cover your outdoor petunias with frost cloth or bring them indoors. Temperatures below freezing will kill them in a jiffy.
While your tomato fruit plants can survive in non-freezing conditions, temperatures below 55°F can still cause damage to your tomato plants.