When can you put tomatoes outside in Colorado?

Answered by Tom Adger

In Colorado, the weather can be quite unpredictable, especially in the spring when we are transitioning from winter to summer. As a result, determining the best time to put tomatoes outside can be a bit tricky. However, there are some general guidelines to follow.

Typically, tomato transplants should be planted outside after the danger of frost has passed. This usually occurs around late May or early June in most parts of Colorado. However, it’s important to keep in mind that this is just a general guideline and can vary depending on your specific location and microclimate.

When deciding whether it’s safe to plant tomatoes outside, you’ll want to pay attention to the nighttime temperatures. Ideally, they should be consistently in the low- to mid-40s at the lowest. This ensures that the plants won’t be exposed to freezing temperatures, which can cause damage or even kill them.

Additionally, it’s crucial to consider the daytime temperatures as well. Tomato plants thrive in warmer conditions, so you’ll want to wait until daytime highs are at least in the upper 50s. If you plant them too early and the temperatures remain consistently cool, below 55 degrees Fahrenheit, it can stunt the growth of the plants and reduce yields.

I remember a time when I planted my tomato transplants too early in the season. We had a week of unusually cool temperatures, and it had a noticeable impact on the plants. They seemed to be struggling and didn’t grow as vigorously as I had hoped. It was a valuable lesson to wait for warmer weather before putting tomatoes outside.

To summarize, in Colorado, it’s generally safe to put tomato transplants outside after the danger of frost has passed, which is usually around late May or early June. Night temperatures should be in the low- to mid-40s at the lowest, with daytime highs at least in the upper 50s. However, keep in mind that a week of cool daytime temperatures below 55 degrees Fahrenheit can stunt plant growth and reduce yields. It’s always better to err on the side of caution and wait for warmer weather before planting tomatoes outside.