US Grow Zones

Pasco, Washington: planting zone & frost dates

Last updated · Sources: PRISM/OSU 2023 ZIP zone listings; NOAA NCEI 1991–2020 Climate Normals (station USW00024163); U.S. Census Bureau — see methodology

Pasco is in USDA plant hardiness zone 7a, where the average coldest winter night reaches 0 to 5°F (-17.8 to -15.0°C). The typical last spring frost is around May 2 and the first fall frost around Oct 4.

Hardiness zone7A0 to 5°F
Last spring frostMay 230% chance of frost after
First fall frostOct 430% chance of frost before
Growing season168 daysmedian frost-free days

Frost dates

ProbabilityLast spring frost (32°F)First fall frost (32°F)
Safer (10% risk)May 10Sep 28
Typical planning date (30% risk)May 2Oct 4
Median (50%)Apr 27Oct 11

How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.

Frost data comes from NOAA station PASCO TRI CITIES AP, WA (USW00024163), 0.2 mi (0.4 km) from the city center and 7 ft higher than the city center (+2 m). Record used for the 1991–2020 normals: 21 years.

Frost probability in spring and fall, Pasco, WAChance of a 32°F frost in Pasco, WA, NOAA 1991–2020. Spring: the chance of another frost falls from 90% on Apr 8 to 10% on May 10. Fall: the chance that the first frost has arrived rises from 10% on Sep 28 to 90% on Oct 27.0%50%100%Spring: later frostMar 15Apr 15May 1530%: May 2Fall: frost arrivedOct 1Oct 15Nov 1Nov 1530%: Oct 432°F frost28°F hard freezeplanning date
Shaded areas show the chance of a 32°F frost: falling through spring, rising through fall. The dashed line is the 28°F hard-freeze curve. Data: NOAA 1991–2020 Normals, station USW00024163.
Frost-free growing season in Pasco, WA1 in 10 risk: May 10 to Sep 28 (141 days); 3 in 10 risk: May 2 to Oct 4 (155 days); Median (50%): Apr 27 to Oct 11 (167 days); No 28°F freeze: Apr 7 to Oct 23 (199 days). In 9 of 10 years the 32°F-free season is at least 148 days.Frost-free days, spring to fallJFMAMJJASOND1 in 10 risk141 days3 in 10 risk155 daysMedian (50%)167 daysNo 28°F freeze199 days
Frost-free window at three risk levels, plus the window between 28°F hard freezes. Read about what the probabilities mean.

Why your yard may differ from the station: microclimates.

Hardiness zone across Pasco

All 1 ZIP code covering Pasco is in zone 7a.

ZIP codes in Pasco and their zones
ZIPZoneShare of city land
993017a100.0%

Vegetable planting calendar for Pasco

Dates are counted from the 30%-risk frost dates above (last frost May 2, first frost Oct 4). Shift a week later in cold spots or low-lying ground.

CropStart indoorsTransplant / plant outDirect sowFall crop sow/plant
TomatoMar 7 – Mar 21May 9 – May 23——
PepperFeb 21 – Mar 7May 16 – May 30——
LettuceMar 21 – Apr 4Apr 18 – May 9Apr 4 – May 16Jul 26 – Aug 23
Green Beans——May 9 – Jun 13Jul 12 – Jul 26
Sweet Corn——May 9 – Jun 6—
Zucchini & Summer SquashApr 4 – Apr 11May 9 – May 23May 9 – May 30Jul 12 – Jul 26
CucumberApr 4 – Apr 11May 16 – May 23May 9 – May 30Jul 12 – Jul 26
Carrot——Apr 11 – May 16Jul 12 – Jul 26
OnionFeb 7 – Feb 21Apr 4 – Apr 18——
Potato—Apr 4 – Apr 25——
BasilMar 21 – Apr 4May 16 – May 30May 16 – Jun 6—
Spinach——Mar 21 – Apr 18Aug 9 – Sep 6
KaleMar 7 – Mar 21Apr 4 – Apr 25Apr 4 – Apr 25Jul 26 – Aug 23
BroccoliMar 7 – Mar 21Apr 18 – May 9—Jul 12 – Jul 26
Peas——Mar 21 – Apr 11Jul 26 – Aug 9
EggplantFeb 21 – Mar 7May 16 – May 30——
CabbageMar 7 – Mar 21Apr 4 – Apr 18—Jul 12 – Jul 26
Radish——Mar 28 – May 16Aug 23 – Sep 20
Strawberry—Apr 4 – Apr 25——
Beets——Apr 11 – May 23Jul 26 – Aug 9

Nearby cities in Washington

More: all Washington cities · other zone 7a cities: Louisville, KY, Wichita, KS, Cleveland, OH, Lexington, KY, St. Louis, MO, Boise, ID, Amarillo, TX, Providence, RI

Pasco gardening questions

When is the last frost in Pasco, WA?

Plan around May 2. At NOAA's Pasco Tri Cities Airport, WA station, 0.2 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Apr 27, and after May 10 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 7. The 90% and 10% dates are 32 days apart, close to the 36-day median for cities on this site.

When should I plant tomatoes in Pasco, WA?

Start seeds indoors Mar 7 – Mar 21 and set transplants outside May 9 – May 23, once nights stay above 50°F and the soil is near 60°F. That leaves 155 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.

How long is the growing season in Pasco?

About 168 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 148 days, and in 1 year in 10 it runs 189 days or more. In fall there is a 10% chance of frost by Sep 28 and a 30% chance by Oct 4. That is the shortest of the 18 Washington cities on this site.

When should I plant a fall garden in Pasco?

Count back from the first fall frost (Oct 4): transplant broccoli Jul 12 – Jul 26; sow kale Jul 26 – Aug 23; sow lettuce Jul 26 – Aug 23; sow radishes Aug 23 – Sep 20. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Oct 23. How the math works: succession and fall planting.

Did Pasco's hardiness zone change on the 2023 map?

No. Going by the zone that covers most of the city's land, Pasco is zone 7a on both the 2012 and the 2023 USDA maps (PRISM/OSU ZIP listings). About 42% of U.S. ZIP codes kept their half-zone in 2023. Why the 2023 map is warmer.

How does Pasco compare with Kennewick, WA?

Pasco is zone 7a and Kennewick is zone 7b. The typical last spring frost in Pasco (May 2) comes about 30 days later than in Kennewick, WA (Apr 2), 5 miles away, and the first fall frost is Oct 4 versus Oct 25. Pasco sits about 156 ft lower, which explains part of the gap. The two cities use different NOAA stations.