Fairspell: Weather Windows

How long should you wait to mow after rain?

There is no set number of hours: wait until the lawn has dried out, the RHS says ^[2]. Purdue prefers the afternoon, once the blades are dry ^[1]. Where a ride-on mower leaves muddy tracks, Purdue suggests a push mower until the soil dries ^[1]. Mississippi State says to keep heavy ride-on mowers off fine-textured soils until they have drained and dried ^[6]. Mowing wet grass clumps the clippings, packs down the soil and can spread turf disease ^[1][2][3].

Why wet grass is a problem

The sources name four kinds of trouble:

• Clumps: Purdue suggests mowing when the leaf blades are dry to reduce clumping ^[1].
• Damaged turf and packed soil: the RHS says mowing wet grass can damage the turf and compact the soil ^[2].
• Disease: Mississippi State advises against mowing a wet lawn, to reduce the spread of disease and soil compaction ^[3].
• Slipping: Iowa State warns that you are more likely to slip in wet grass with a walk-behind mower, and a Mississippi State safety newsletter says wet grass raises the risk of a mower sliding, losing control or rolling over ^[4][5].

How to tell the lawn is dry enough

None of these sources gives a number of hours, so check the lawn itself:

• The grass blades are dry. Purdue suggests the afternoon; the RHS says later in the day, once the lawn has dried out ^[1][2].
• The mower leaves no muddy tire tracks. If a ride-on mower does, Purdue suggests a push mower on those wet areas until the soil dries, to avoid ruts that can damage the turf for good ^[1].
• On fine-textured soils, keep heavy ride-on mowers off until the soil has drained and dried. Wet soil packs down much more easily, Mississippi State says ^[6].

If the rain will not stop

Purdue prefers dry grass, but says it is fine to mow wet turf or mow in light rain, and better to mow wet than to wait until the grass is 8 inches (about 200 mm) tall ^[1][7]. Its tips for wet grass:

• Sharpen the blade first ^[7].
• Set the mower high, especially if the grass is taller than usual ^[1][7].
• Use side discharge rather than a mulching attachment, and send the clippings onto grass you have already cut ^[7].
• Break up clumps by mowing again, even twice in one day, or bag the clippings for mulch or compost ^[7].
• Clean under the mower deck afterwards ^[1].

After storms leave the grass much taller than normal, Mississippi State suggests raising the cutting height a little for the first mowing, then mowing at the normal height a couple of days later ^[6].

How Fairspell's Mow the lawn template handles this

Fairspell is an iPhone app that searches the hourly forecast for a run of hours that suits an activity. Its Mow the lawn template looks for:

• At least 2 hours in a row to mow.
• 12 dry hours before the window. An hour counts as wet when the forecast shows 0.3 mm (about 0.01 in) of rain or more, and Fairspell trims or drops a window that fails the check.
• No hour in the window with more than 0.5 mm (0.02 in) of rain forecast.
• A higher score when rain chance is 0 to 10%, temperature is 50 to 75°F (10 to 24°C) and wind is 0 to 12 mph (0 to 20 km/h).

The sources above give signs, not hours, so 12 hours is Fairspell's own default. The template reads forecast rain, not dew or how wet the ground is, so check the blades and the soil before you start. To wait longer or shorter, open the activity and change Dry before under Rain safety; it goes from 0 to 24 hours.

Mow the lawn is one of the templates in the free version, which allows two activities and a three-day forecast. Fairspell Full, a one-time purchase ($7.99 in the US), adds unlimited activities and a ten-day forecast. Forecasts change, so a window is guidance, not a guarantee.

Get it on the App Store

Sources

1. How to Mow Now That it has Stopped Raining, Purdue University Turfgrass Science, accessed 2026-10-16
2. Lawn Mowing Guide, Royal Horticultural Society, accessed 2026-10-16
3. Good Cultural Practices Help Reduce Lawn Diseases, Mississippi State University Extension Service, accessed 2026-10-16
4. Mowing Safely, Iowa State University Extension and Outreach, accessed 2026-10-16
5. Dawg Tracks Safety Newsletter: Mower Safety, August 2026, Mississippi Agricultural and Forestry Experiment Station and MSU Extension Service, accessed 2026-10-16
6. Lawn care after storm related rainfall, Mississippi State University Extension Service, accessed 2026-10-16
7. Mowing Wet Grass, Purdue University Turfgrass Science, accessed 2026-10-16

Published 2026-10-16. Updated 2026-10-16.