When Is The Best Time To Spray Weed Killer

When Is The Best Time To Spray Weed Killer?

We're an affiliate

We hope you love the products we recommend! Just so you know, we may collect a share of sales or other compensation from the links on this page. Thank you if you use our links, we really appreciate it!

When Is The Best Time To Spray Weed Killer

Timed wrong, spraying weed killers won’t have any effect, making the whole ordeal of clearing weeds from your property more frustrating. We discuss when is the best time to spray weed killer in this post.

Agriculturists and horticulturists alike have relied upon weed killers more and more over the decades to help manage weeds.

While they offer a promising solution for weeds growing on softscapes and hardscapes of all sizes, most weed killers need to be sprayed at a specific time of the day to work effectively.

In other words, if timed wrong, spraying even the best weed killer on the market won’t work.

But learning about the different kinds of weed killers and learning to time spray weed killers isn’t difficult at all. In this post, we discuss when is the best time to spray weed killer.

When Is the Best Time to Spray Weed Killer?

Understanding how different types of weed killers work is key to learning the best times to apply them. So here’s a quick look at the different types of weed killer sprays and how they work:

  • Pre-emergent weed killers: These products create a chemical barrier in the soil or gravel they’re applied to, preventing weed growth. In other words, these herbicides are applied before the weeds appear – they don’t kill pre-existing weeds.

  • Post-emergent weed killers: These are the more popular variety of weed killers formulated to wither and destroy existing weeds. Post-emergent weed killers are of two types: selective and non-selective.

    • Selective/systemic weed killers: When sprayed, weeds absorb these herbicides through the leaves, eventually reaching the root. The weed killers then take effect, withering the weeds from the root, eliminating them at the source. Since absorption takes time, these products take a few days to a week to show results.

    • Non-selective/contact weed killers: Non-selective weed killers only wither the parts of the weeds they’re sprayed upon. These don’t eliminate vegetation by the root, meaning the weeds will grow back in a few weeks. While less effective, these begin showing results in a matter of hours.

There’s no right or wrong type of weed killer. Instead, you must choose between them according to your priorities.

Best Time of Day to Spray Weeds

Weeds have dew on them early in the morning, which dilutes the herbicide and causes runoff, reducing its efficacy significantly. However, as the sun rises, the dew evaporates. The best time of day to spray weeds is between 11 a.m. and 3 p.m.

Bear in mind that pre-emergent weed killers can be applied at any time of day. However, post-emergent weed killers of both kinds must be sprayed midday for best results.

Safety Warning

The majority of weed killers in the market have toxic chemicals in them that can cause burns. Before spraying, wear long pants and a long-sleeved shirt, and use gloves and safety goggles to protect yourself.

Best Time of Year to Spray Weeds

best time of year to spray weeds

The best time of year to spray weeds is in the spring. Weeds begin germinating in spring, so spraying pre-emergent weed killers will stop them from growing in the first place.

Then, in the final month of spring, you can spray post-emergent weed killers to get rid of the young weeds that managed to grow.

But here’s the thing: weeds attack your property all through the year. Waiting till the spring to spray post-emergent weed killer doesn’t always make sense. Here are some strategies to help you manage weeds in other seasons.


The fall is the second-best season to spray weeds. Weeds typically struggle to survive the winter, so spraying them in the fall will ensure they don’t grow back for a long time. Spraying weeds twice in the middle of spring, two weeks apart, is the best way to kill weeds for good.


Weed sprays are the least effective in the winter. However, the weed killer should work effectively as long as you spray the weeds in the afternoon when there’s sunshine.

Spraying weeds on a rainy or snowy day isn’t worth the effort. The conditions won’t be right for the weed killer to work, and, likely, you will not see any results.


Spraying weeds in the summer can be tricky. Often, the midday heat causes the spray to evaporate, reducing the amount of herbicide the weeds absorb. Therefore, it’s best to wait until the end of the season to spray weed killers since it isn’t as warm.

Spraying weeds in late summer also reduces the amount of work you may need to put in the next spring.

What Is the Best Temperature To Spray Weed Killer?

The best temperature to spray weed killer is between 65°F and 85°F.

What is the Best Weather to Spray Weed Killer?

Pleasant weather, when the temperature is between 65°F and 85°F, and the wind isn’t blowing too hard, is the best weather to spray weed killer.

Rain dilutes weed killer, so it’s best to wait at least 24 hours after rain for the plants to dry before spraying any weed killer. If you live where it often rains, get a weed killer that is rainproof in under three hours, and spray it on a warm afternoon.

Windy weather isn’t ideal for spraying weed killers either. The weed spray may blow to other parts of your property or kill plants you don’t want to kill. Spraying weed killers on a still day is the right way to go. Protecting the plants you don’t want to be affected by the weed killer with cardboard is also a good idea.

Extremely hot weather leads to the weed killer spray evaporating quickly, and the spray may freeze in extremely cold weather. Therefore, avoid spraying weeds in extreme temperatures.

Top 3 Weed Killers for Killing Weeds Any Time of Year

You can buy any of these weed killers to get rid of weeds in any season. You don’t have to worry about when is the best time to spray weed killer. Just make sure you apply them when the temperature is above 60°F.

1. RoundUp Ready-to-Use Weed & Grass Killer III

Roundup Ready-To-Use Weed & Grass Killer III

The RoundUp Weed & Grass Killer III comes with a comfort wand, and since it’s ready to use, all you have to do is turn the nozzle and spray the weeds. The sprayer is battery-powered and comes with a battery included, so no manual action is required.

The spray works on various surfaces – you can spray it on flower beds, vegetable gardens, patios, walkways, driveways, and most other parts of your property.

One bottle of these will allow you to spray approximately 400 square feet. But the best part about the weed killer spray is that it kills the weeds at the root. In addition, the company offers a money-back guarantee, which makes it that much more reliable.

The spray becomes rainproof ten minutes after spraying, and the weeds begin to wilt within three hours of application. Its effectiveness and ease of use make this RoundUp spray hard not to recommend.

  • Ready-to-use formula
  • Comfortable spray wand
  • Rainproof in 10 minutes
  • Weeds begin to wilt in three hours
  • The strong chemical smell after application

2. Green Gobbler 20% Vinegar Weed & Grass Killer

Green Gobbler 20% Vinegar Weed & Grass Killer

While the Green Gobbler Weed & Grass Killer is an organic weed killer, it’s just as effective as a chemical-based weed killer and will destroy all sorts of weeds.

The spray is safe to use anywhere there are weeds, and you don’t have to worry about it affecting your family or pet’s health. The OMRI-listed product kills weeds 24 hours after application.

The company offers a 30-day money-back guarantee. If the spray doesn’t work as expected, you can get a full refund, no questions asked.

The only disadvantage with this organic weed killer spray is that it comes with a manual spray. However, getting your hands on the best weed-killer sprayer will reduce the amount of labor you need to put into pumping and spraying.

  • OMRI-listed organic weed killer
  • Results in 24 hours
  • 30-day money-back guarantee
  • Manual spray

3. Ortho GroundClear Year-Long Vegetation Killer

Ortho GroundClear

If you’re looking to get rid of weeds from hardscapes, the Ortho GroundClear Year-Long Vegetation Killer is an excellent option. The product starts killing weeds in an hour and keeps them from regrowing for up to one year.

You can use it on gravel areas, sidewalks, along a fence or curb, or in the parking area. It’s also one of the best weed killers for driveways.

The company recommends spraying the weed killer on a sunny day when the temperature is above 60°F.

  • Rainproof in one hour
  • It makes your property weed-free for up to one year
  • The smell dissipates in 20 minutes
  • High-quality sprayer
  • Built for spot-spraying

Takeaway: When to Spray Weeds?

So, when is the best time to spray weed killer?

It’s any warm, sunny spring day, between 11 a.m. and 3 p.m. Fall is a nice season to spray weeds, too. Just make sure you time it just right – spraying the weeds in the middle of the fall. The winter will ensure that the weeds don’t survive.

But you can pick any pleasant day that’s not too windy and spray anytime between late morning and early afternoon.

Related Posts