Question 1

Why doesn’t this show my weather station?

Accepted Answer

Diggin Up does not look up the nearest weather station and treat that as your frost date. Our data starts with weather station readings; however since weather stations can be very far away, mathematical models calculate the effects of elevation and terrain, and produce a more appropriate figure for all nearby locations.

Question 2

Does this account for my local microclimate?

Accepted Answer

The models capture local terrain and elevation differences better than a distant station, at roughly 2.5 miles (4 km) resolution. Yard-scale effects—a warm south wall, a frost pocket, urban heat, or wind shelter—are finer than that grid. Use these dates as a planning baseline, then check local forecasts and what you know about your own site.

Question 3

What’s the difference between frost, freeze, and hard freeze dates?

Accepted Answer

Frost (36°F) is the planning default for last and first frost dates. Freeze (32°F) and Hard freeze (28°F) are colder risk thresholds when you want more conservative freeze guidance. Use Compare thresholds above the results to switch which temperature the tool uses for the dates you see.

Question 4

When does frost occur?

Accepted Answer

Frost typically forms on clear, calm nights when heat radiates from the ground into the atmosphere, most often in spring and fall. Cloudy or windy nights mix warmer air and usually reduce frost risk even when the calendar looks similar.

Question 5

Can frost happen after my last frost date?

Accepted Answer

Yes. Frost dates are historical averages at a given probability, not a guarantee that frost will not return. Always check your local forecast before planting tender crops or removing season protection.

Question 6

How much can frost dates vary within a ZIP code?

Accepted Answer

ZIP codes can span enough elevation and terrain that frost dates differ by several days from one spot to another. Fact: 99557 in Alaska is a whopping 13,590 square miles! Enter your current location in the calculator location and we will pull the most localized data for your estimation.

Question 7

What can I plant before the last frost?

Accepted Answer

Cool-season and cold-hardy crops—such as peas, spinach, radishes, carrots, onions, and lettuce—are often sown or set out before the average last frost. Tender warm-season plants (tomatoes, peppers, cucumbers, basil, and most annual flowers) wait until after the last frost date for your chosen threshold.

Question 8

What is growing season length?

Accepted Answer

Growing season length is the span of days between the last spring frost and the first fall frost for a given temperature threshold. A longer frost-free window means more time for warm-season crops; a shorter one favors cool-season plantings and season-extension techniques.

Question 9

Do frost dates mean the same thing as my hardiness zone?

Accepted Answer

No. USDA hardiness zones describe winter cold extremes that perennial plants must survive. Frost dates mark the typical start and end of the frost-free growing season for annual planting and protection—season bookends, not the same as your zone number.

First and Last Frost Dates 2026 by Location or ZIP Code