What to do in Waterloo now
Waterloo is in cool-season grass country. Dates are typical for this spot, worked out from 23 years of weather at Waterloo Municipal Ap; each status uses this year's soil estimates.
Cool-season: tall fescue, Kentucky bluegrass, perennial ryegrass, fine fescue
- Crabgrass pre-emergent Closed Apr 17 Typical: Apr 13 – Apr 262-inch soil held 55°F for a week from Apr 17, so crabgrass was sprouting. Next window: about Apr 13 – Apr 26, 2027.
- Seed or overseed Last days · under 50°F by Nov 7 Typical: Sep 8 – Oct 19The window usually closes by Oct 19, but this fall has kept 4-inch soil at 59°. Seed only if you can keep it moist, and expect slower germination as soil cools.
- Late-fall feeding Final feeding due now Typical: Oct 28 – Nov 20Not too late. Feed on your normal fall schedule; the last feeding of the year goes down when 4-inch soil falls to about 50°F (typically Oct 28) and before it reaches 40°F (typically Nov 20).
Warm-season: bermudagrass, zoysia, St. Augustine, centipede, bahia
- Crabgrass pre-emergent Closed Apr 17 Typical: Apr 13 – Apr 262-inch soil held 55°F for a week from Apr 17, so crabgrass was sprouting. Next window: about Apr 13 – Apr 26, 2027.
- Seed or sod Wait for late spring Typical: May 25 – Sep 8Warm-season seed needs 4-inch soil at 65°F or more, and seedlings need the rest of summer to establish. Next window opens about May 25.
- Fall pre-emergent (Poa annua) Germinating since Sep 16 Typical: By Sep 74-inch soil fell below 70°F on Sep 16, when annual bluegrass begins to sprout. A pre-emergent now only stops later flushes; plan to apply by about Sep 7 next year.
- Dormancy and last feeding Any day now Typical: Around Oct 19Warm-season grass slows and browns once 4-inch soil stays under 55°F, typically Oct 19. Make the last nitrogen feeding at least a month before that.
The last 60 days and the week ahead
Waterloo soil is 14° warmer than normal for Nov 3, warmer than on 99% of those dates since 2005, and 15° warmer than a year ago.
The green line is our estimate of the daily average soil temperature 2 inches down, driven by temperatures at Waterloo Municipal Ap, 8 km from the city center. The dashed part runs the National Weather Service forecast through the same model. Hover or tap for any day.
2-inch soil, estimated From the NWS forecast Normal Normal range (8 years in 10)
Show the numbers
| Date | 2-inch soil | 4-inch soil | Air high / low | Normal (2 in) |
|---|---|---|---|---|
| Oct 21 | 54° | 56° | 74° / 42° | 50° |
| Oct 22 | 56° | 58° | 77° / 45° | 49° |
| Oct 23 | 58° | 59° | 75° / 50° | 49° |
| Oct 24 | 61° | 61° | 77° / 56° | 48° |
| Oct 25 | 60° | 61° | 70° / 48° | 48° |
| Oct 26 | 59° | 60° | 65° / 48° | 47° |
| Oct 27 | 58° | 59° | 62° / 50° | 47° |
| Oct 28 | 60° | 61° | 78° / 49° | 46° |
| Oct 29 | 57° | 59° | 64° / 38° | 45° |
| Oct 30 | 53° | 56° | 53° / 37° | 45° |
| Oct 31 | 54° | 56° | 62° / 52° | 45° |
| Nov 1 | 55° | 57° | – / – | 45° |
| Nov 2 | 57° | 58° | 64° / 57° | 45° |
| Nov 3 | 59° | 59° | 68° / 58° | 44° |
| Nov 4 (forecast) | 55° | 57° | 52° / 45° | 44° |
| Nov 5 (forecast) | 52° | 55° | 53° / 38° | 44° |
| Nov 6 (forecast) | 48° | 51° | 48° / 30° | 44° |
| Nov 7 (forecast) | 47° | 50° | 51° / 35° | 44° |
| Nov 8 (forecast) | 46° | 49° | 56° / 36° | 44° |
| Nov 9 (forecast) | 48° | 50° | 62° / 40° | 43° |
| Nov 10 (forecast) | 48° | 50° | 60° / 41° | 43° |
Which grass grows in Waterloo
Waterloo winters are cold enough (January averages 20°F) that cool-season grasses, mostly Kentucky bluegrass, tall fescue and perennial ryegrass, make up most lawns. They grow in spring and fall and slow down in summer heat.
Waterloo soil through the year
Weekly 2-inch estimates for 2026 so far against 2025 and the normal for each week. The red lines mark 50°F, when crabgrass pre-emergent should be down, and 65°F, when warm-season seed sprouts well.
2026 2025 Normal (2005–2025) 8 years in 10
Normal by month
| Month | 2 in | 4 in | Air |
|---|---|---|---|
| Jan | 32° | 33° | 20° |
| Feb | 32° | 34° | 24° |
| Mar | 38° | 39° | 37° |
| Apr | 48° | 49° | 49° |
| May | 60° | 61° | 62° |
| Jun | 72° | 73° | 72° |
| Jul | 75° | 77° | 75° |
| Aug | 73° | 75° | 72° |
| Sep | 67° | 68° | 65° |
| Oct | 53° | 55° | 52° |
| Nov | 40° | 42° | 37° |
| Dec | 33° | 34° | 25° |
Soil: average of our daily estimates, 2005–2025. Air: NOAA 1991–2020 normals for the station.
Typical lawn dates in Waterloo
Each date is when the soil estimate (or the air, for freezes) crossed the threshold, year by year since 2005. “Early” and “late” are the 10th and 90th percentile years, so 8 years in 10 fall between them.
| Event | Typical | 2026 |
|---|---|---|
| Last spring freeze (32°F) | May 4 | May 11 |
| Crabgrass model: 250 growing degree days | Mar 31 | Mar 19 |
| Pre-emergent window opens (2-inch soil 50°F) | Apr 13 | Apr 14 |
| Crabgrass begins to sprout (2-inch soil 55°F) | Apr 26 | Apr 17 |
| Cool-season lawns start growing (4-inch soil 55°F) | Apr 22 | Apr 17 |
| Warm-season seeding opens (4-inch soil 65°F) | May 25 | May 21 |
| Cool-season seeding opens (4-inch soil under 70°F) | Sep 8 | Sep 17 |
| Cool-season seeding ends (4-inch soil under 55°F) | Oct 19 | Nov 8 |
| Warm-season grass goes dormant (4-inch under 55°F) | Oct 19 | Nov 8 |
| First fall freeze (32°F) | Oct 11 | Oct 17 |
| Roots stop feeding (4-inch soil under 40°F) | Nov 20 | not yet |
Where these numbers come from
There is no soil sensor in most cities, so we estimate it. Shallow soil follows air temperature with a lag of a few days, and runs a little warmer than the air in fall. We fitted that relationship to 190 USDA soil-sensor stations; on years held out of the fit, the estimate was off by 3.3°F on an average day, and it put the spring 55°F date within a median of 3 days. Read the methodology.
Weather: RCC ACIS station KALO (WATERLOO MUNICIPAL AP), daily data since 1950. Forecast: National Weather Service, DMX office, issued Nov 4, 2026, 5:01 AM EST. Last observed day: Nov 3, 2026.
Waterloo questions
What is the soil temperature in Waterloo today? Our estimate for Nov 3 is 59°F at 2 inches and 59°F at 4 inches, as a daily average. Early-morning soil runs a few degrees cooler than that, and afternoon soil warmer.
When should I put down crabgrass pre-emergent in Waterloo? Apply when 2-inch soil holds about 50°F and before it holds 55°F. That has typically been Apr 13 to Apr 26 in Waterloo. For 2026 the window closed on Apr 17.
Is it too late to overseed in Waterloo? Last days · under 50°F by Nov 7. The window usually closes by Oct 19, but this fall has kept 4-inch soil at 59°. Seed only if you can keep it moist, and expect slower germination as soil cools.
Is it too late to fertilize in Waterloo? Final feeding due now. Not too late. Feed on your normal fall schedule; the last feeding of the year goes down when 4-inch soil falls to about 50°F (typically Oct 28) and before it reaches 40°F (typically Nov 20).
When is the last frost in Waterloo? The last 32°F night of spring has typically come around May 4, and as late as May 16 in 1 year in 10. The first fall freeze typically arrives around Oct 11.
Why 2 inches and 4 inches? Crabgrass and most weed seeds sprout in the top inch or two, so pre-emergent timing follows 2-inch soil. Grass seed and roots respond to the slightly steadier soil at about 4 inches.
How accurate is this? It is a model, not a probe in your yard. Expect about 3–4°F of difference on a given day; shade, slope, mulch and irrigation all move real soil. The dates and trends are more reliable than any single day.