The last frost date is a guess. A good guess, but still.

The last frost date for your area is an average. Specifically, it's the date by which, historically, there's been a fifty percent chance of frost. Which means: half the time, you still get frost after it.

That's not a flaw in the system. It's statistics. An average drawn from decades of weather is useful, but it's not a schedule. May 7th being your last frost date doesn't mean the frost stops reading the calendar. It means the odds are improving around that time, fast. Not that they've gone to zero.

A few things worth knowing when you're working with frost dates:

The fifty-percent date is your middle marker, not your finish line. Most extension services also publish the ten-percent and ninety-percent dates — the dates by which you'd expect frost only one time in ten, and the dates by which frost is almost certainly behind you. Knowing the range is more useful than knowing the midpoint.

Your land has its own dates. Valley bottoms, creek hollows, north-facing slopes, and spots shaded by trees run colder than the surrounding landscape — often three to five degrees colder on a clear calm night. If your garden sits in a low spot, subtract a few degrees from the official forecast and add a few days to your safe planting window. Your spot is not the reporting station.

The forecast matters more than the date. The week you're actually planting, a five-day forecast is far more actionable than the last frost average. If the average says you're probably clear but the forecast shows thirty-eight degrees Thursday night, trust Thursday. The average is a planning tool. The forecast is what's actually happening.

Row covers buy you margin. Not infinite margin — a hard freeze will kill what it kills — but a frost cloth rated to twenty-eight degrees can turn a thirty-two-degree night into a won night. If you're pushing the window because the plants are ready and the beds are ready and you can feel spring even if the calendar won't admit it, a cover gives you running room.

There is no date when the risk goes to zero. Even in June, most places have seen a frost at least once in their records. What changes isn't the possibility — it's the probability. And probability is all we ever really have with weather.

Plant into the window that makes sense for your place. Check the forecast. Have the cloth ready. The date is a guide, not a promise.

Take it easy.