USDA Zone Guides
Your USDA hardiness zone is set by your area's average annual extreme minimum winter temperature, in ten-degree-Fahrenheit bands from Zone 1 (coldest) to Zone 13 (warmest). It's the single most useful piece of information for timing a vegetable garden, because it implies a realistic frost window - and frost, not the calendar month, is what actually determines when tender crops can safely go in the ground.
What Each Zone Guide Covers
Every zone page states the zone's average annual extreme minimum temperature range, a typical frost window implied by that range, and a month-by-month outline of what's realistic to plant and when across a full growing season. See the Methodology page for exactly how these ranges are sourced and how often they're reviewed.
A Zone Is a Long-Term Average, Not a Forecast
It's worth being direct about a common misunderstanding: your zone describes a long-term climate average, not a prediction for this specific year's weather. A late-spring cold snap can still damage tender transplants in any zone, and a zone number alone doesn't account for microclimates within your own yard (a south-facing wall, a low frost pocket, a shaded slope). The Frost-Date Lookup tool is built around this distinction explicitly - it reports typical historical ranges, not a forecast for the coming season.
If you don't already know your zone, check your zone against your local agricultural extension office's published map, or use the Frost-Date Lookup tool to estimate a working frost window directly.
Microclimates Within Your Own Zone
Two gardens in the same official zone can still behave differently - a south-facing wall that radiates stored heat, a low spot where cold air pools on a still night, or a shaded corner that stays several degrees cooler than the rest of the yard. None of that shows up in a zone number, which is why experienced gardeners often treat their zone's frost window as a starting estimate to refine with their own observation over a season or two, not a fixed rule to follow blindly.
Zone Number Alone Doesn't Determine Summer Heat
It's worth knowing that USDA zones are defined entirely by winter minimum temperature, not by summer heat, humidity, or rainfall - two gardens in the same zone can have very different summer growing conditions. A zone number tells you about frost timing specifically; it doesn't tell you whether your summers are hot and dry, hot and humid, or mild, which matters separately for things like disease pressure and whether heat-sensitive crops like lettuce will bolt early in your area.
Once you know your zone, the When to Plant section and the Planting Calendar Generator tool both use it directly to give you crop-specific timing rather than a generic "early spring" instruction that means something different everywhere.