Cut if the crop will reach baling moisture inside a rain-free window, and if tonight's dew point leaves enough spread to dry. Two numbers and one forecast decide it.
Should I cut hay today?
window HAY WINDOWchecked 2026-09-16rots yes — these figures moveresponsible Windrow Field Manual (a named masthead, not a person)
What you need Tonight's forecast low and dew point; a moisture reading on the standing crop or the last cut; the drying window you expect from experience.
[['Three or more rain-free days, dew point well below the forecast low', 'Yes', 'The window is wide and the rewetting risk is small'], ['Two rain-free days, dew point close to the forecast low', 'Yes, and bale in the evening', 'You will lose the early morning to dew either way'], ['One rain-free day', 'Only with a wide swath and wind', 'Thin margin; the second day usually decides it'], ['Rain inside 36 hours', 'No', 'A single rain event on curing hay costs more than the delay']]
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Steps
- Read tonight's forecast low and dew point. If the low will come within two or three degrees of the dew point, the crop rewets overnight and the morning is gone.
- Count the rain-free days in the forecast. Two full days is the working minimum for a swath left to dry in place; three is comfortable.
- Set the swath width for the weather you expect, not the weather you want. A wider swath dries faster and rewets faster.
- Cut in the morning so the crop has the whole day, and plan the baling pass for the evening, when the dew point spread is widest.
- Decide now when you will stop. A crop cut for a window that then closes is worth less than a crop left standing.
What the drying curve does to the plan
| Time since cutting | Typical moisture, grass | What is happening |
|---|---|---|
| 0 hours | 75–80% | The plant is still respiring and losing water fast |
| 6 hours | 55–65% | Surface water is gone; stem moisture is the limit |
| 24 hours | 30–40% | Drying slows sharply; this is where tedding pays |
| 48 hours | 18–25% | Approaching baling range for most bale sizes |
The number people skip
The dew point is the number that decides the evening. A forecast of two clear days is worth much less than a forecast of two clear days with a wide dew-point spread, and the second is not visible in the rain probability at all.
The manual holds that the evening baling window is under-used and the morning one is over-rated. The spread between the air temperature and the dew point is usually widest in the late afternoon and early evening, which is exactly when the crop is driest.
Where the numbers come from
- S1Hay Crops: Cereals and Grasses (Chapter V), FAO Agricultural Services Bulletin 154supports the crop and weather conditions that make cutting worthwhile
- S2Hay Crops: Cultivation Methods (Chapter III), FAO Agricultural Services Bulletin 154supports the cultivation and cutting practice the decision sits inside
- S3Executive Summary, Hay and Straw Conservation, FAO Agricultural Services Bulletin 154supports the field-drying summary the two-day rule is drawn from
One link, one document. No home pages, no search results, no bare domains.
Put this page down Put this page down once you have the two numbers and the forecast in front of you. The rest is arithmetic.