Most of us know a temperature lower than 32°F would kill tender vegetables like tomatoes, peppers, melons, and cucumbers. Home gardeners would wait to plant those crops after the last frost passed, but commercial farmers may take the risk of planting earlier to capture early-season premium prices. Farmers use various strategies, i.e., high tunnels, low tunnels, floating row covers, and even cups, to protect the early-planted crops from frost/freeze temperatures.
Some plants (tomatoes) may be able to survive the less-than-optimal conditions. They hold in the field and wait to grow after the temperature rise. However, the risk of losing the plants under less-than-optimal conditions is much higher with cucurbits (cantaloupes, watermelons, cucumbers). To plant these crops in the early season, farmers should check the extended forecast, ensure that there are no frost/freeze events, and check soil temperatures. Cucurbits are best grown when soil temperatures are above 70°F. It may not always be possible to wait when soil temperatures rise above 70°F to plant, but at least wait to plant when soil temperatures are stable above 60°F. This video tells a story of early-planted watermelons and their suffering from low temperatures.