Average weather days by month
Bars show the average lost days per month across the history window. The tick above each bar is the 90th percentile, the bad year you should be ready to document.
Your schedule, month by month
Wind risk on module and crane days
Abnormally Severe Weather line
Many EPC contracts only give you time for weather that is more than two standard deviations from the 25-year daily average for that calendar month, by NOAA's record. This is that line for the station shown. Weather short of it is yours to carry in the baseline schedule.
Typical year, month by month
Rain is tracked three ways: rain days, heavy rain days, and average rainfall. The other columns show average working days per month that tripped each rule. Max is the worst single year. *Wind appears only when you enter module or crane dates, and only inside those dates.
Schedule and contract language
That is what the weather will do. What does your contract give you for it?
The weather clause, the notice window, and who owns the float are somewhere in a few hundred pages you signed. Axion reads every page of your contracts and project documents and answers in seconds, with the source attached.
Method and source
- Data: daily precipitation, snowfall, and high and low temperature from the NOAA Global Historical Climatology Network Daily (GHCN-Daily) record for the station shown, served by the NOAA Regional Climate Centers. Wind comes from NOAA NCEI daily summaries for the nearest airport station that reports it.
- High-wind days: wind is counted only on the module install and crane dates you enter. A day counts when the fastest 2-minute wind reaches the sustained threshold and the whole day averaged at or above the second threshold, so a single passing gust front does not cost you a day. The daily record cannot show how many hours the wind held, so this is a proxy for duration, not a measured two-hour window.
- Wind risk: each task's dates are replayed against every complete year. The figures are how many working days in that window met the wind rule, and how many of those were not already lost to rain, cold or heat.
- Station choice: the nearest station whose record covers the history window is picked first. You can switch to any other nearby station, including the one your contract names.
- Complete years only: a year is used only if rain and temperature were recorded on at least 90% of its days. Years left out are listed with the result. A missing day inside a year that is used is not counted as a weather day.
- Counting: a working day is a weather day if it meets the rain, snow, cold or heat threshold, or the wind rule on a module or crane date. Dry-out days are the days after a heavy rain. Monthly counts are computed for each year, then averaged. Rainfall totals use every calendar day.
- Construction window: the same calendar window is replayed against every complete year in the record. The average, 90th percentile, and worst case come from those replays, for the whole window and for each of its months. A first or last month that is not a full month is marked partial.
- Abnormally Severe Weather line: for each calendar month, the average and standard deviation of the daily values are taken over every day of that month in the complete years of the record. The line is the average plus the number of standard deviations in your contract, or minus for cold. "Past the line" counts weather days that are also beyond it. "You carry" counts weather days that fall short of it. The two add up to your weather days. Contracts word this test differently, so check the measure, the station and the period against yours.
- Not counted: lightning stand-downs, holidays, and site-specific conditions such as flooding or access roads.
What is a weather day in a construction contract?
A working day when weather stops or materially slows the work on the critical path. Most contracts expect you to carry the normal number of weather days in your baseline schedule. You only get a time extension for weather beyond that normal number.
How many weather days should I put in my schedule?
Carry the historical average for the project location, counted month by month over the months you will actually be building, using the same thresholds your contract uses. Then look at the 90th-percentile year so you know what a bad year costs before you sign.
What counts as abnormal or unusually severe weather?
Weather beyond what the record says is normal for that location and that month. If the record says to expect six weather days in April and you lose ten, the four extra days are the ones you can usually claim, provided you gave notice the way the contract requires.
My contract defines abnormal weather by standard deviations. What does that mean?
Some contracts only treat a day as abnormally severe when it is more than two standard deviations from the 25-year daily average for that calendar month. Daily rain is mostly zeros with a few big days, so that line usually sits near or above an inch of rain in a day. An ordinary rain day that stops work is below it, and stays in your schedule at your risk. This planner shows the line for each month and how many of your weather days fall short of it.
Why does my contract reference NOAA?
Many owner contracts name a NOAA weather station as the baseline for normal weather. This planner uses the same NOAA station records and shows you which station it used and how far it is from your site. If your contract names a different station, pick it from the list.
Nothing you enter is stored by Axion. Weather records: NOAA National Centers for Environmental Information and the NOAA Regional Climate Centers. ZIP lookup by Zippopotam.us.