US Grow Zones

Meridian, Idaho: planting zone & frost dates

Last updated · Sources: PRISM/OSU 2023 ZIP zone listings; NOAA NCEI 1991–2020 Climate Normals (station USC00106305); U.S. Census Bureau — see methodology

Meridian 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 5 and the first fall frost around Oct 6.

Hardiness zone7A0 to 5°F
Last spring frostMay 530% chance of frost after
First fall frostOct 630% chance of frost before
Growing season164 daysmedian frost-free days

Frost dates

ProbabilityLast spring frost (32°F)First fall frost (32°F)
Safer (10% risk)May 18Sep 29
Typical planning date (30% risk)May 5Oct 6
Median (50%)Apr 29Oct 13

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 NAMPA SUGAR FACTORY, ID (USC00106305), 8.8 mi (14.1 km) from the city center and 121 ft lower than the city center (-37 m). Record used for the 1991–2020 normals: 22 years.

Frost probability in spring and fall, Meridian, IDChance of a 32°F frost in Meridian, ID, NOAA 1991–2020. Spring: the chance of another frost falls from 90% on Apr 15 to 10% on May 18. Fall: the chance that the first frost has arrived rises from 10% on Sep 29 to 90% on Oct 28.0%50%100%Spring: later frostApr 1Apr 15May 1May 1530%: May 5Fall: frost arrivedOct 1Oct 15Nov 1Nov 1530%: Oct 632°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 USC00106305.
Frost-free growing season in Meridian, ID1 in 10 risk: May 18 to Sep 29 (134 days); 3 in 10 risk: May 5 to Oct 6 (154 days); Median (50%): Apr 29 to Oct 13 (167 days); No 28°F freeze: Apr 11 to Oct 25 (197 days). In 9 of 10 years the 32°F-free season is at least 142 days.Frost-free days, spring to fallJFMAMJJASOND1 in 10 risk134 days3 in 10 risk154 daysMedian (50%)167 daysNo 28°F freeze197 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 Meridian

All 2 ZIP codes covering Meridian are in zone 7a.

ZIP codes in Meridian and their zones
ZIPZoneShare of city land
836427a55.7%
836467a44.2%

Vegetable planting calendar for Meridian

Dates are counted from the 30%-risk frost dates above (last frost May 5, first frost Oct 6). Shift a week later in cold spots or low-lying ground.

CropStart indoorsTransplant / plant outDirect sowFall crop sow/plant
TomatoMar 10 – Mar 24May 12 – May 26——
PepperFeb 24 – Mar 10May 19 – Jun 2——
LettuceMar 24 – Apr 7Apr 21 – May 12Apr 7 – May 19Jul 28 – Aug 25
Green Beans——May 12 – Jun 16Jul 14 – Jul 28
Sweet Corn——May 12 – Jun 9—
Zucchini & Summer SquashApr 7 – Apr 14May 12 – May 26May 12 – Jun 2Jul 14 – Jul 28
CucumberApr 7 – Apr 14May 19 – May 26May 12 – Jun 2Jul 14 – Jul 28
Carrot——Apr 14 – May 19Jul 14 – Jul 28
OnionFeb 10 – Feb 24Apr 7 – Apr 21——
Potato—Apr 7 – Apr 28——
BasilMar 24 – Apr 7May 19 – Jun 2May 19 – Jun 9—
Spinach——Mar 24 – Apr 21Aug 11 – Sep 8
KaleMar 10 – Mar 24Apr 7 – Apr 28Apr 7 – Apr 28Jul 28 – Aug 25
BroccoliMar 10 – Mar 24Apr 21 – May 12—Jul 14 – Jul 28
Peas——Mar 24 – Apr 14Jul 28 – Aug 11
EggplantFeb 24 – Mar 10May 19 – Jun 2——
CabbageMar 10 – Mar 24Apr 7 – Apr 21—Jul 14 – Jul 28
Radish——Mar 31 – May 19Aug 25 – Sep 22
Strawberry—Apr 7 – Apr 28——
Beets——Apr 14 – May 26Jul 28 – Aug 11

Nearby cities in Idaho

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

Meridian gardening questions

When is the last frost in Meridian, ID?

Plan around May 5. At NOAA's Nampa Sugar Factory, ID station, 8.8 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 29, and after May 18 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 11. The 90% and 10% dates are 33 days apart, close to the 36-day median for cities on this site.

When should I plant tomatoes in Meridian, ID?

Start seeds indoors Mar 10 – Mar 24 and set transplants outside May 12 – May 26, once nights stay above 50°F and the soil is near 60°F. That leaves 154 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 Meridian?

About 164 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 142 days, and in 1 year in 10 it runs 186 days or more. In fall there is a 10% chance of frost by Sep 29 and a 30% chance by Oct 6. That ranks 2nd longest of 3 Idaho cities on this site.

When should I plant a fall garden in Meridian?

Count back from the first fall frost (Oct 6): transplant broccoli Jul 14 – Jul 28; sow kale Jul 28 – Aug 25; sow lettuce Jul 28 – Aug 25; sow radishes Aug 25 – Sep 22. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Oct 25. How the math works: succession and fall planting.

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

No. Going by the zone that covers most of the city's land, Meridian 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 Meridian compare with Boise, ID?

Both are in zone 7a. The typical last spring frost in Meridian (May 5) comes about 5 days later than in Boise, ID (Apr 30), 9 miles away, and the first fall frost is Oct 6 versus Oct 14. The two cities use different NOAA stations.