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Germination timing based on current soil temperature readings from your nearest monitoring station.
The 2-inch soil temperature near Hilo, HI is currently 54.9°F (56.3°F at 4 inches), measured in the ground at the Silver Sword monitoring station (21.9 mi away). That is about 3°F cooler than typical for this date.
Seed now: this is the prime window of the year. Soil has cooled back into the cool-season germination range, and tall fescue, Kentucky bluegrass, and perennial ryegrass establish roots before winter with less weed competition than spring.
Based on long-term station averages, the 2-inch soil near Hilo typically crosses the cool-season seeding threshold (50°F) around May 30. Use these dates as a starting guide, but always confirm with a current soil thermometer reading.
These windows are computed from Hilo's multi-year soil-temperature climatology, so they reflect this location rather than a regional average. Treat them as a starting plan and confirm with current readings.
Typical 2-inch soil temperature by month near Hilo, from multi-year station averages, with the seeding verdict for each grass family. Confirm against the current reading above before you put seed down.
| Month | Typical 2" soil temp | Cool-season seeding | Warm-season seeding |
|---|---|---|---|
| January | 44°F | Too cold | Too cold |
| February | 45°F | Too cold | Too cold |
| March | 45°F | Too cold | Too cold |
| April | 46°F | Too cold | Too cold |
| May | 48°F | Too cold | Too cold |
| June | 55°F | Good; fall is better | Too cold |
| July | 56°F | Good; fall is better | Too cold |
| August | 56°F | Prime window | Too cold |
| September | 53°F | Prime window | Too cold |
| October | 51°F | Prime window | Too cold |
| November | 47°F | Too cold | Too cold |
| December | 45°F | Too cold | Too cold |
Cool-season grasses share a seeding band, with tall fescue wanting the warmer end of it; warm-season grasses run higher. Germination floors come from university extension guidance and the band tops are our establishment cutoffs; the dates come from Hilo's own station climatology.
| Species | Seeding soil temp | Days to germinate | Soil typically ready | Right now |
|---|---|---|---|---|
| Bermudagrass | 75–90°F | 10-30 | Rarely reached | Too cold |
| Zoysia | 75–90°F | varies | Rarely reached | Too cold |
| Buffalograss | 75–90°F | 14-30 | Rarely reached | Too cold |
| Centipede | 75–90°F | varies | Rarely reached | Too cold |
| Kentucky bluegrass | 60–70°F | 14-30 | Rarely reached | Germinates slowly |
| Tall fescue | 60–70°F | 7-12 | Rarely reached | Germinates slowly |
| Perennial ryegrass | 60–70°F | 5-10 | Rarely reached | Germinates slowly |
| Fine fescue | 60–70°F | 7-14 | Rarely reached | Germinates slowly |
“Right now” compares each species’ band to the current 2-inch reading of 54.9°F. “Soil typically ready” is the first calendar day the long-term station average climbs into that species’ seeding band.
Cool-season grasses (tall fescue, Kentucky bluegrass, perennial ryegrass) germinate best when the 2-inch soil temperature stays between 50°F and 65°F. The ideal window is early to mid-spring, or early fall when soil cools back into this range. Fall seeding has less weed competition and more consistent moisture.
Warm-season grasses (Bermuda, zoysia, St. Augustine, centipede) need soil temperatures of65°F or higher for germination. These grasses are best seeded in late spring through early summer when soil has fully warmed.
Use a soil thermometer at 2 inches depth, measured mid-morning after the sun has warmed the surface. Take readings in several spots and average them. One warm day does not mean soil is ready; look for a sustained trend across 3–5 days.
Enter your city or ZIP code for real-time 2-inch soil temperatures from the nearest USDA monitoring station.