How It Works

Good Project Day answers a simple question: is this a good day for my project? A normal weather app shows the weather. It doesn’t tell you that tonight’s dew will streak your fresh paint, or that a 40% chance of rain tomorrow morning is too soon for driveway sealer.

The data

When you enter a ZIP code, we convert it to coordinates using U.S. Census Bureau ZIP Code Tabulation Area data. Your browser then requests the hourly gridded forecast for that point directly from the National Weather Service API: temperature, dew point, relative humidity, wind speed and gusts, probability of precipitation, and precipitation amounts, on a grid of about 2.5 km.

The scoring

Each project has a set of rules based on typical manufacturer instructions and industry guidance, such as American Concrete Institute cold- and hot-weather concreting practices and herbicide label conventions. For every possible start time each day, we check:

• Temperature, humidity, dew point spread, and wind during the work window
• Rain during the work, and in the hours before (wet surfaces) and after (drying and curing)
• Overnight lows and freezes in the 12–72 hours after you finish
• Project-specific checks, such as the concrete evaporation rate and rain amounts for watering in fertilizer

Any hard limit that fails makes the day No. Softer concerns make it Maybe. If everything checks out, it’s Good. We show the best window and every reason, so you can make the final call.

Limitations

Forecasts are uncertain, especially beyond 3 days. Local conditions such as shade, sun exposure, surface temperature, and wood moisture can differ a lot from the forecast. Treat this as planning guidance, check again the day before, and always follow your product label.