What A Temperature Chart Is, And How It Can Help You Plan Your Garden Better

A temperature chart gives you a rough guide to how the air (and soil) temperatures in your yard change throughout the course of a year. When making one, you typically include details like the average high and low temperature for each month or the expected dates of your first and last frost. Since so much of a plant's growth from when a seed germinates to when it will go dormant or die depends on temperature, charting this seemingly simple detail can make planning your garden much easier.

You'll have a better understanding of just how long your growing season is, as well as when to sow seeds or put out transplants based on their temperature preferences. While often used for planning a vegetable garden, you can also use it to get a sense of what kinds of ornamental plants might do well in your yard. With an entire year of average temperatures charted out, you can see at a glance whether your climate might be too hot or too cold for a given species.

A temperature chart can even help you tailor general gardening advice to your climate. A task that should be done in "early spring" might mean March for one gardener and May for another. While every year is different, making your own temperature chart gives you an easy way to figure out approximately when to plan for different gardening tasks. Keep reading to learn how to make a temperature chart and tips for using one to make gardening decisions like when the best time to plant corn is or when you should stop mowing your lawn.

At a minimum, a temperature chart should include a column with the names of all 12 months, a column for the average high air temperature, one for the average low, and one for the season. You also want to indicate the average first and last frost dates somewhere near the months where they occur. To find the average frost dates for your region, go to the Old Farmer's Almanac and enter your zip code. To get the temperatures for each month, use the National Weather Service database to find averages for your area.

Instead of standard season names, you'll label each month as either cold, cool, warm, or hot. Roughly speaking, cool season crops like air temperatures in the 40 to 75 degrees Fahrenheit range, while warm season crops prefer temperatures ranging from about 50 to 80 degrees. Hot season crops would be anything that needs temperatures consistently above 65 degrees. And your cold season is any month where the average temperatures are too cold for any of those plants.

Base your labels for each month on how the average highs and lows fit into those ranges. In cooler months, for example, distinguishing cool season from cold season could be based on when the average high temperatures are within the range of cool season crops, but there's still a risk of frost. Warm season months, meanwhile, would be those where all chance of frost has passed and even the average low temperatures are within range. Any months where the average high is above 80 can be your hot season.

A temperature chart is most useful for making sure you correctly time and prepare your garden after the last winter frost. Since some veggies prefer cooler temperatures while others prefer warmer temperatures, you can time your planting based on when your local climate is most likely to suit their preferences. Within each category, you can further divide plants into those that are cold hardier or those that are more heat tolerant. Cold hardy cool season crops can be planted even earlier than other cool season crops, as they'll be able to withstand an occasional frost. Likewise, your more heat tolerant warm season veggies can be planted later than others, since they'll be able to endure the higher temperatures of your hot season.

Aside from timing your planting, you can also use the chart to make other gardening decisions. For example, if you read that you should prune a particular tree in late winter, just before it begins growing again in spring, your temperature chart can give you a much more precise idea of exactly which month fits that description. Similarly, if you have a long warm and hot season, you might want to trade your cool-season grass for a warm-season species. When choosing new species to add to your garden, use your temperature chart the same way. Instead of relying on USDA hardiness zones, which only tell you the coldest possible temperature in your region, you can research the plant's preferred temperature range and see if it's a match for your climate.