what temperature is too cold to water grass

What Temperature is Too Cold to Water Grass?

In Lawn & Garden by Jamie

Did you know that just because it’s winter, you may still have to water your lawn? If you’re up in the north like I am, where winters last a third of the year, you can (and should) put away your sprinklers for the winter. But if winter temperatures stay above 40F (4C), you’re left wondering, is the temperature too cold to water grass?

It’s too cold to water grass when ground temperatures drop to 40F (4C) or below, or if there’s frost on the grass. Watering when there’s frost on the grass can end up freezing and destroying the grass blade, harming the grass. So long as your lawn continues to grow and not go dormant, you should water your lawn at a reduced rate.

Should I water my lawn in the winter?

So long as the ground temperature remains above 40F (4C), and especially if you still need to mow your lawn, your lawn needs water, even in December.

Winter watering differs from summer watering. In the summer, you have to apply much more water every week as the heat evaporates a good portion of it. In winter, without the heat, you only need a fraction of that water to keep your grass sated. Grass typically needs 1-inch of water per week.

How often that is depends on your soil type and the weather, so if you’re not sure, check the soil to see if the upper layer is still damp. Avoid watering the grass when there’s frost on your lawn as that’s a clear sign that it’s too cold.

If your winter weather consists of rain and drizzle, then you probably don’t have to worry about watering at all.

And if your grass has gone dormant (the whole lawn has grown brown), then it’ll need even less water (only once every month or two).

And, of course, if snow covers your lawn, you don’t need to water.

Should I water my lawn before a freeze or after frost?

Water can protect your lawn during cold weather, but only under certain conditions. If you see a freeze coming in over 24 hours (whether an unexpected dip in an otherwise mild winter or the start of the winter freeze), check to see if your soil is dry and needs watering. If it does, give your lawn a thorough soaking. When the freeze comes, the water in the soil will freeze too, protecting the roots.

This is especially important when you live in an area with a dry autumn climate and long, freezing winters. The water in the soil will last the grass all winter.

Don’t water your grass when there’s frost still on it. When regions that usually have a mild or warm winter get an unexpected cold snap, some homeowners panic and try to spray off the frost to save their grass, but only end up creating an ice rink on their front lawn. If you have cool-season grass, it’ll be fine so just leave it be.

Warm-season grass, like Bermuda and St Augustine grass, are susceptible to frost damage. When temperatures drop below 50F, Bermuda grass goes dormant. Below 30F, the stem and leaves die. If daytime temperatures remain near 70F, Bermuda grass will survive chilly nights as low as 34F. St Augustine grass is more prone to frost damage than Bermuda.

You can protect your grass by giving it a thorough soaking 24 hours ahead of the freeze and letting your grass grow longer before it goes dormant in the winter. Taller grass has deeper root systems, which helps even warm-season grasses survive freezes. (The same goes for cool-season grasses!)

How cold is too cold for sprinklers?

If night-time temperatures go below 40F (4C), then it’s too cold for sprinklers and automatic irrigation systems. Freezing temperatures below 32F (0C) can damage your irrigation system if they’re not properly winterized. Any water remaining in the irrigation pipes will freeze and expand, causing burst pipes and damage to other components.

To winterize your automatic irrigation system:

  • Check for leaking or broken heads and nozzles and make any necessary repairs or replacements.
  • Turn off the water with the water shutoff valve.
  • Manually open the irrigation valves to let out any remaining water or pressure.
  • Release any remaining water through the drain valves.
  • Hire a certified irrigation professional to “blow-out” the system using a commercial air compressor. Consumer air compressors don’t have enough pressure to do a good job and it’s easy to accidentally damage another part of your system. Not all irrigation systems work the same, either. The professional can also help you with the next step, preparing the backflow preventer for winter.
  • Prepare the backflow preventer for winter by turning the ball valves to a 45-degree angle to release any remaining water.
  • If there’s any exposed, above-ground pipes, wrap it in insulation foam and/or buy a backflow blanket.
  • Open the drain valve again for any remaining water and leave it open. (Place a bucket underneath to catch any water during the winter.)
  • Make sure that your irrigation controller is in the OFF position.

This process should be done a week before the first freeze of winter.

If you live in an area with mild to warm winters and temperatures unusually dip below 40F at night for a short period, wrap any exposed pipes in towels overnight to protect them.

Can you Water Grass at 40 Degrees Fahrenheit?

40 degrees is the lowest temperature that you want to water grass. Any lower, and grass will go dormant and water freezes. That’s fine if the water has properly soaked into the soil, but a little devastating if you find that you’re creating ice rinks on your lawn.

How to Protect New Sod or Newly Germinated Grass from Frost?

You just installed your new sod or have been growing a new lawn from seed when disaster strikes: there’s an unexpected frost in the forecast! There is one technique that may save your grass, although it only works if it’s one frosty night and daytime temperatures are still warm. Use room temperature water to heat the vulnerable grass enough to survive the frost. Again, this only works for a brief time. If the water freezes on the grass, that’ll be enough to kill it.

Final Thoughts

It is important to know what temperature is too cold to water grass. If you have snowy winters, then keep an eye on the weather report to give your lawn a deep drink before the first freeze of winter. If you have warmer, mild winters, slow down your regular watering schedule. And if an expected frost approaches in over 24 hours, give your lawn a deep drink to help protect the roots during the freeze.