Outdoor project weather: frequently asked questions

Enter your ZIP code on the home page and you get a Good, Maybe or No for ten outdoor projects across the next 7 days, built from the hourly National Weather Service forecast for your spot. Each project also has its own page with the best time window for every day, for example deck staining or pouring concrete.

Good means every check passes for at least one work window that day. Maybe means the job is doable but something needs watching, such as a 30–49% chance of rain while you work or a cool night after. No means at least one limit is likely to make the job fail, such as a 50% or higher chance of rain during the dry period the project needs, or a freeze on fresh concrete. Each verdict lists the reasons. The methodology page has every rule.

Most weather failures happen while a coating or slab cures, not while you work: rain the night after staining, dew on fresh paint at dusk, a freeze two days after a pour. So each project checks the hours after you finish too, up to 72 hours for concrete. The weather timing guide explains why.

It is the chance that measurable rain (0.01 inch or more) falls at your location in that period, not the share of the day it rains. The forecast treats 30% or more in a period that must stay dry as a caution and 50% or more as likely rain. More in What does a 40% chance of rain mean?

The forecast covers 7 days. The first one to three days are the most reliable, so use days 4–7 to pick a likely day and check again the evening before. How to read an hourly forecast shows what to look at.

No. The forecasts come from the U.S. National Weather Service, which covers the United States, and the lookup accepts U.S. ZIP codes only. You can also use your device location if you are in the U.S.

The forecast wants the 24 hours before you start to be dry, and after a soaking rain 48 hours of dry, breezy weather is safer. Shaded boards and the undersides dry last. Before you open the can, sprinkle a little water on the boards: if it soaks in within about a minute, the wood is dry enough. Is your deck dry enough to stain? covers the test, and How long after rain can you stain, paint or seal? compares the wait for each job.

The deck stain forecast needs 24 hours with no likely rain after you finish and prefers 48. Water-based stains are often dry to the touch in a few hours in warm weather, while oil-based stains can stay soft for a day or more, especially when it is cool or humid. Your product label gives the exact rain-ready time.

Yes, while the days reach at least 50°F and the nights stay up. The forecast marks a day No if it drops below 40°F within 12 hours of finishing and warns below 50°F. Short days and heavy morning dew are what usually end the season. See How late in the fall can you stain, paint or seal?

The forecast allows up to 90°F and prefers 55–85°F. Deck boards in full sun can run much hotter than the air, which makes stain flash-dry and leave lap marks. On hot days stain early in the morning or in shade, a few boards at a time. Surface vs. air temperature explains the gap.

Evening staining is risky because dew often forms on the wet stain as the air cools. The forecast needs humidity at or below 85%, the air at least 5°F above the dew point, and no dew in the 4 hours after you finish, so its work window starts between 9 AM and 2 PM. Dew point for painting and staining shows how to check it.

For standard exterior latex, yes: most need 50°F. Paints labeled for low-temperature use can go on at 35°F, and the temperature has to stay above that minimum while the paint dries, including overnight. The exterior paint forecast marks a day No below 35°F and tells you when only a low-temperature paint will work.

The forecast allows up to 90°F and prefers 50–85°F. In heat, paint dries before it levels, which leaves lap marks and brush marks, and siding in direct sun is hotter still. Follow the shade around the house: paint the west side in the morning and the east side in the afternoon.

No. Fog means the air is at its dew point, so surfaces are wet or close to it, and paint applied then can blister, streak or fail to bond. Wait until the fog lifts and the surface is dry, and the air is at least 5°F above the dew point. That is the rule the forecast uses. See How long exterior paint needs before it rains for what moisture does to fresh paint.

Usually not. Fresh latex paint hit by evening dew can develop sticky, brown or soapy streaks (surfactant leaching). Finish early enough that the paint has a few hours to dry before the air cools toward the dew point. The forecast checks the 4 hours after you finish for dew.

The concrete forecast needs at least 40°F during the pour, marks a day No if a freeze is forecast within 48 hours, and Maybe if lows drop below 40°F within 72 hours. Concrete has to be protected from freezing until it reaches about 500 psi, which takes about two days for a normal mix in cool weather. Insulated blankets and accelerated mixes extend the season. See Pouring concrete in hot or cold weather.

Avoid it. Rain during placing and finishing adds water to the surface, which weakens it and leads to dusting and scaling. The forecast marks a day No if rain is likely (50% or more) during the pour window. Keep plastic sheeting on site in case a shower arrives early.

Once the surface has set hard enough that rain won’t mark it, usually a few hours in warm weather and longer in cool weather, rain does little harm and can even help curing. The forecast wants 8 dry hours after you finish and prefers 24.

The same limits apply: don’t pour into frozen ground, and keep the concrete above freezing for about two days. Fast-setting post mixes also slow down in the cold. On a cool day, pour in the morning so the concrete gets the warmest hours.

Wind, low humidity and heat pull water off the surface faster than it can rise through the slab, which causes plastic shrinkage cracks. The forecast estimates the evaporation rate every hour and flags anything above 0.2 lb/ft²/hr, the threshold in the American Concrete Institute hot-weather guide. The methodology page shows the formula.

Most asphalt sealers need 50°F or higher while you apply them and for the next 24 hours, and the driveway sealing forecast uses exactly that rule. A sunny 55°F afternoon followed by a 38°F night is a No. Cold nights, not cold days, usually end the season. See How late in the fall can you seal?

The pavement must be fully dry, including low spots and cracks where water sits. The forecast checks the 24 hours before you start and warns if rain is expected. After a heavy rain, a full sunny day is usually enough on asphalt. See How long after rain can you stain, paint or seal?

Late spring through early fall, on a sunny day between 60°F and 90°F with no rain for at least 24 hours (ideally 48). Start mid-morning once dew has dried so the sealer gets the afternoon sun: the forecast looks for a 3-hour window starting between 10 AM and 1 PM. The seasonal calendar shows when that window opens where you live.

Only if the product has time to become rainfast first. Labels for common glyphosate weed killers give rainfast times from about 30 minutes to several hours depending on the formula, so read yours. The weed killer forecast looks for 6 dry hours after spraying, which covers most products.

It is better not to. Evening air is often dead calm, and calm air near the ground can trap fine spray droplets and carry them sideways (a temperature inversion). Dew also dilutes the spray. The forecast’s window runs from 7 AM to 7 PM and wants a steady 3–10 mph breeze. More in Best weather to spray weed killer.

The forecast allows up to 90°F and prefers 60–85°F. In heat, weeds under drought stress take up less herbicide, and some products (for example ester forms of 2,4-D) can turn to vapor and drift onto nearby plants. On hot days spray in the morning.

Before crabgrass germinates, which starts when the soil 2 inches down stays around 55°F for several days. In many areas that lines up with forsythia blooming. Most granular pre-emergents then need rain or irrigation to move them into the soil. See When to apply crabgrass preventer.

It depends on your grass and the forecast. Cool-season lawns (fescue, bluegrass, ryegrass) get most of their feeding in fall and some in spring. Warm-season lawns (Bermuda, zoysia, St. Augustine) are fed from late spring through summer while they grow. The lawn fertilizer forecast checks the weather side: temperature, wind, and whether rain will water it in or wash it away.

About a quarter inch moves granular fertilizer off the grass blades and into the soil. The forecast counts 0.1–0.75 inch within 48 hours as a bonus, and marks a day No if an inch or more is forecast within 24 hours, because that much can wash fertilizer into storm drains.

Yes. Mowing first actually helps, because granules reach the soil instead of sitting in tall grass. Leave the clippings and water the fertilizer in if no light rain is coming.

Wood siding and decks usually need 48 hours of dry weather, longer in cool, humid or shaded spots. Brick and concrete can hold water for days. Do the water drop test on wood or use a moisture meter. Is your deck dry enough to stain? covers both. Then check the paint forecast, which also wants 24 dry hours before you start.

Give it at least 24 hours of dry weather, and 48 if it is cool or the slab is shaded. Sealer over damp concrete or asphalt can turn cloudy or peel. Use the driveway sealing forecast to find the next dry spell.

Not with water in it. Water left in the pump or hoses can freeze and crack them. Drain it, run a pump protector through it, and store it somewhere above freezing. The pressure washing forecast warns when it will freeze within 12 hours of washing. More in Pressure washing in cold weather.

Only if the slab and air stay warm enough. Most kits need at least 50°F, many prefer 60°F, and the floor has to stay warm while it cures. The epoxy forecast marks a day No if it drops below 45°F within 24 hours and warns below 55°F. A concrete slab warms much more slowly than the air, so a heated garage needs time to bring the floor up. See Surface vs. air temperature.

Tape a square of clear plastic to the slab and leave it for at least 16 hours. Moisture or a dark patch underneath means water is coming up through the concrete, and epoxy will likely lift. The forecast checks the air (humidity at or below 85% and the slab at least 5°F above the dew point), not moisture inside the slab, so do both checks.

An unheated garage follows the outdoor temperature, and you need the door open for ventilation while you work. Humid outdoor air then condenses on a cold slab, which causes a cloudy, greasy film (amine blush) and poor adhesion. Dew point for painting and staining explains the 5°F rule.

Most latex and hybrid exterior caulks need 40°F or higher, and the caulking forecast uses 40°F as its minimum. Some 100% silicone sealants can go on colder if the surface is dry and free of frost. Gaps are at their widest in cold weather, so don’t overfill. See What temperature can you caulk outside?

No. Caulk won’t bond to a wet joint. The forecast wants 12 dry hours before you start, the air at least 5°F above the dew point, and 6 dry hours after you finish, preferably 24.

Most spray paints need 50°F for both the air and the part, and metal left outside overnight stays colder than the air for hours. Bring the piece inside to warm up, and keep the can at room temperature. The spray paint forecast uses 50–90°F with 60–85°F preferred.

Usually humidity. Fast-evaporating solvents cool the surface, and in humid air moisture condenses into the wet paint and leaves a milky haze (blushing). The forecast wants humidity at or below 85%, ideally under 65%, and the air at least 5°F above the dew point.

Most spray paints are dry to the touch within an hour in mild weather but need much longer to harden. The forecast looks for 6 dry hours after you finish and prefers 12. See How long paint needs before it rains.