The best time to plant tomatoes is after the danger of frost has passed in your area, when the soil and air temperatures are reliably warm. Here are some key points to consider:

• Tomatoes are sensitive to frost and temperatures below 32ºF (0ºC) can kill or seriously damage them.
• Find out the average last frost date for your specific location; this is when you can safely plant tomatoes outdoors.
• For long growing seasons (170+ frost-free days), it's recommended to plant tomatoes about two weeks after the last frost date to avoid late-season cold snaps and bad weather.
• In average growing seasons (120-170 frost-free days), plant tomatoes 1-2 weeks after the last frost date and choose varieties that mature in less than 100 days if you have a shorter season.
• Nighttime temperatures should ideally be consistently above 50°F (10°C) for planting outdoors.
• Tomato seeds are often started indoors 6-8 weeks before the average last frost date and then transplanted outside after the frost risk passes.
• For greenhouse growing, planting can be done earlier once the inside temperature is consistently above 15°C.

In summary, to successfully plant tomatoes, wait for your local frost danger to pass, ensuring both soil and night temperatures are warm enough, then plant your seedlings or transplanted plants outdoors. Starting seeds indoors about 6-8 weeks before the last frost date helps produce strong plants ready for transplanting. This timing advice will vary depending on your local climate zone and frost dates, so finding your area's frost date is essential for precise timing.