Frost dates for 98027Issaquah, WA
The average last spring frost in Issaquah is April 23 and the average first fall frost is November 1, giving a typical growing season of about 193 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 23
- Average first fall frost
- Nov 1
- Growing season
- 193 days
Safer after May 13 (1-in-10 risk)
Possible by Oct 17 (1-in-10 risk)
First frost typically in 0 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | Apr 25 · May 10 · May 27 | Oct 1 · Oct 16 · Oct 31 | 156 days | 100% |
| Frost / freeze (32°F) | Apr 3 · Apr 23 · May 13 | Oct 17 · Nov 1 · Nov 22 | 193 days | 100% |
| Hard freeze (28°F) | Feb 27 · Mar 24 · Apr 21 | Nov 2 · Nov 22 · Dec 15 | 243 days | 100% |
Planting calendar for Issaquah
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Mar 23 – May 29 |
| Tomatoes | Transplant outdoors | May 9 – Jul 12 |
| Peppers | Start seeds indoors | Mar 23 – Apr 23 |
| Peppers | Transplant outdoors | May 23 – Jun 23 |
| Eggplant | Start seeds indoors | Apr 9 – May 8 |
| Eggplant | Transplant outdoors | May 23 – Jun 23 |
| Cucumbers | Sow outdoors | May 23 – Jul 22 |
| Summer squash | Sow outdoors | May 9 – Jun 23 |
| Winter squash & pumpkins | Sow outdoors | May 23 – Jun 23 |
| Snap beans | Sow outdoors | May 9 – Aug 14 |
| Sweet corn | Sow outdoors | May 9 – Jul 12 |
| Watermelon & cantaloupe | Sow outdoors | May 23 – Jun 23 |
| Okra | Sow outdoors | May 16 – Jun 8 |
| Peas | Sow outdoors (spring) | Mar 23 – May 8 |
| Potatoes | Plant outdoors (spring) | Mar 23 – May 23 |
| Onions | Start seeds indoors (spring) | Feb 9 – Mar 8 |
| Onions | Transplant outdoors (spring) | Apr 9 – May 8 |
| Broccoli | Start seeds indoors (spring) | Mar 5 – Apr 8 |
| Broccoli | Transplant outdoors (spring) | Apr 9 – May 8 |
| Broccoli | Start seeds indoors (fall) | Jul 2 – Jul 12 |
| Broccoli | Transplant outdoors (fall) | Aug 1 – Aug 12 |
| Cabbage | Start seeds indoors (spring) | Feb 23 – Mar 23 |
| Cabbage | Transplant outdoors (spring) | Mar 23 – Apr 23 |
| Cabbage | Start seeds indoors (fall) | Jun 22 – Jul 22 |
| Cabbage | Transplant outdoors (fall) | Jul 22 – Aug 22 |
| Leaf lettuce | Sow outdoors (spring) | Mar 23 – Jun 8 |
| Leaf lettuce | Sow outdoors (fall) | Jul 22 – Sep 7 |
| Spinach | Sow outdoors (spring) | Mar 16 – Apr 29 |
| Spinach | Sow outdoors (fall) | Aug 8 – Sep 12 |
| Radishes | Sow outdoors (spring) | Mar 23 – May 13 |
| Radishes | Sow outdoors (fall) | Jul 22 – Sep 22 |
| Kale | Sow outdoors (spring) | Apr 9 – Apr 29 |
| Kale | Sow outdoors (fall) | Jul 15 – Aug 22 |
| Carrots | Sow outdoors (spring) | Apr 23 – Jun 8 |
| Carrots | Sow outdoors (fall) | Jun 22 – Aug 7 |
| Garlic | Plant outdoors (fall) | Oct 22 – Nov 22 |
Where these dates come from
ZIP code 98027 is matched to the NOAA station Cedar Lake, WA, 21.3 km away, at 1,560 ft elevation (120 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Cedar Lake, WA (used) | 1,560 ft | Apr 23 | Nov 1 |
| Landsburg, WA | 535 ft | Apr 20 | Oct 25 |
| Snoqualmie Falls, WA | 440 ft | Mar 30 | Nov 7 |
| Renton Muni Ap, WA | 29 ft | Mar 13 | Nov 16 |
Frost dates near Issaquah
- Issaquah, WA 98029 · last Mar 30, first Nov 7
- Preston, WA 98050 · last Mar 30, first Nov 7
- Renton, WA 98059 · last Apr 20, first Oct 25
- Hobart, WA 98025 · last Apr 20, first Oct 25
- Sammamish, WA 98075 · last Mar 30, first Nov 7
- Fall City, WA 98024 · last Mar 30, first Nov 7
- Bellevue, WA 98006 · last Apr 20, first Oct 25
- Maple Valley, WA 98038 · last Apr 20, first Oct 25
Frequently asked questions
- When is the last frost in Issaquah, WA?
- For ZIP code 98027, the average last spring frost (32°F) is April 23, based on NOAA 1991-2020 climate normals for the Cedar Lake, WA weather station. There is a 1-in-10 chance of a frost after May 13.
- When is the first frost in Issaquah, WA?
- The average first fall frost (32°F) is November 1. There is a 1-in-10 chance of frost by October 17, so tender plants are at risk from that point on.
- How long is the growing season in 98027?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 193 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.