Research
Are big downpours more common? Days with 1 inch or more of rain, 1991-2025
Cincinnati's official weather station at CVG airport averaged 12.6 days a year with 1 inch or more of rain in 2011-2025, up from 9.5 in 1991-2005, the only one of four long-record stations in our markets where the rise passes a standard trend test (NOAA GHCN-Daily).
By Top Rated Gutters · Published
Homeowners often tell us storms feel heavier than they used to. We counted the days with 1 inch or more of rain in every year from 1991 to 2025 at the official weather station for four of the areas we serve, and compared the first 15 years with the last 15.
Key numbers
9.5 to 12.6 days
Days a year with 1 inch of rain or more at Cincinnati's CVG station, 1991-2005 vs 2011-2025 (+32%).
Source: NOAA GHCN-Daily, CVG airport, Hebron, KY; our count
6.3 to 8.4 days
The same count at South Bend's airport (+34%); the year-to-year swings are too large to call it a trend yet.
Source: NOAA GHCN-Daily, South Bend airport; our count
13.7 to 15.3 days
Atlanta's airport (+12%), with no clear trend across the 35 years. Macon went from 14.4 to 13.7.
Source: NOAA GHCN-Daily, Atlanta and Macon airports; our count
0 of 4
Stations with a clear change in days of 2 inches or more. Those days stayed rare everywhere.
Source: NOAA GHCN-Daily, 1991-2025; Mann-Kendall test
Days a year with 1 inch of rain or more
1991-2005 average2011-2025 average
The table behind the chart
Average days a year at each station. The trend test (Mann-Kendall) asks whether the 35 yearly counts rise or fall more steadily than chance would produce; below 0.05 is the usual bar.
| Area (weather station) | Days with 1 in. or more, 1991-2005 | Same, 2011-2025 | Change | Trend test p-value | Trend, days per decade | Days with 2 in. or more, 1991-2005 / 2011-2025 | Wettest day since 1991 | 1991-2020: our count / NOAA normal |
|---|---|---|---|---|---|---|---|---|
| Atlanta, GAAtlanta Hartsfield-Jackson International Airport | 13.7 | 15.3 | +12% | 1.00 | 0.0 | 2.6 / 3.6 | 6.68 in., 4 Oct 1995 | 14.8 / 14.9 |
| Macon, GAMacon Middle Georgia Regional Airport | 14.4 | 13.7 | -5% | 0.73 | 0.0 | 3.3 / 3.3 | 10.25 in., 5 Jul 1994 | 14.1 / 14.0 |
| Cincinnati, OHCincinnati/Northern Kentucky International Airport (CVG), Hebron, KY | 9.5 | 12.6 | +32% | 0.01 (passes) | 1.1 | 2.1 / 2.0 | 5.02 in., 16 Aug 2018 | 10.8 / 10.8 |
| South Bend, INSouth Bend International Airport | 6.3 | 8.4 | +34% | 0.13 | 0.7 | 1.0 / 0.9 | 7.69 in., 15 Aug 2016 | 7.5 / 7.5 |
Every year’s count for each station is in the CSV download. For storm intensity rather than frequency, see our roof runoff study.
What this means for your gutters
- In Cincinnati, gutters get tested more often. About 3 more days a year with an inch of rain means more days when a partly clogged gutter or a downspout that empties beside the foundation shows it. Cleaning before the wet months and checking where each downspout drains are worth doing every year.
- In Georgia, heavy rain was already routine. Atlanta and Macon averaged 15.3 and 13.7 such days a year in 2011-2025, more than Cincinnati or South Bend, and neither station shows a clear trend. What sizes a gutter there is the intensity of the worst storms, covered in our roof runoff study.
- Plan for the overflow day. Each station's wettest day since 1991 is in the table. Gutters aren't sized for a record storm like those; what matters on such a day is that the overflow spills away from the house, not toward the foundation.
- A count is not a forecast. Four stations over 35 years show what happened at those spots. They do not show why, or what the next decade will bring.
Method
We counted days with 1.00 inch or more, and 2.00 inches or more, of rain (snow counted as melted water) in each calendar year from 1991 to 2025 at four airport weather stations, using NOAA's Global Historical Climatology Network daily records. Values with a NOAA quality flag were left out.
Every station had at least 363 days of rain observations in every year, so no year was dropped. Cumming's cooperative station was left out because 13 of its 35 years have gaps.
We compare the average of 1991-2005 with the average of 2011-2025. To judge whether a change is more than year-to-year noise we ran a Mann-Kendall trend test on all 35 yearly counts; a result below 0.05 is the usual bar for calling a trend. Sen's slope gives the size of the trend in days per decade.
As a check, our 1991-2020 averages match NOAA's own published 1991-2020 normals for days with 1 inch or more to within a few tenths of a day at every station (table below).
Sources
- NOAA NCEI, Global Historical Climatology Network daily (GHCN-Daily), station files. Period: 1 Jan 1991 to 31 Dec 2025.
- NOAA NCEI, U.S. Climate Normals 1991-2020 (days with 1 inch or more, for the cross-check). Period: 1991-2020.
Limits
- One station per area. Heavy rain is patchy, and a storm can soak one side of a county and miss the other.
- A trend at a station is not climate attribution. Station moves, equipment changes and nearby development can all affect a record; we used the records as NOAA publishes them.
- 15-year averages are sensitive to a few very wet or very dry years, which is why the trend test uses every year. Only Cincinnati's rise passes it (p = 0.01).
- The Cincinnati station is CVG airport in Hebron, Kentucky, the official Cincinnati climate site.
- Days of 2 inches or more average a few a year at most, too few to show a clear change in 35 years.
Cite this study
Top Rated Gutters (2026). Are big downpours more common? Days with 1 inch or more of rain, 1991-2025. Published 12 Nov 2026. https://topratedgutters.com/research/heavy-rain-days-trend/
The table is free to download as a CSV file and free to reuse with credit to Top Rated Gutters and a link to this page (CC BY 4.0). The underlying public data stay under their publishers’ own terms.
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