Rodent Complaints in Detroit: Where and When (2023–2026 311 Data)

Complaints by month, 2023 to 2026

September, October and November are shaded so you can see how the autumn months sit against the rest of the year in Detroit.

One caveat about the Detroit data

Detroit publishes Improve Detroit as one rolling layer covering every request type rather than a file per year, so the date filter is applied in the query. It is the smallest series in this set by a wide margin, which is a statement about how Detroit routes rodent reports rather than about how many rodents Detroit has. Small series are also noisier: a single month here moves the annual share far more than the same month would in New York.

Reading the Detroit numbers

Detroit spreads its rodent complaints across 30 ZIP codes, and the load is not spread evenly. The busiest five carry 43% of the three-year total and the busiest ten carry 72%. ZIP 48227 alone logged 676 complaints, about 5.2 times the median ZIP code in the city. It is also the densest, at about 90.1 complaints per square mile across 7.5 square miles, so it leads on both volume and concentration.

Across the year, October (12.37%), September (12%) and August (11.33%) are the three heaviest months, while December (4.37%), January (4.58%) and February (4.62%) are the three lightest. May through October alone accounts for roughly 66% of a Detroit year. Year to year the totals ran -8.9% into 2024, then -2.1% into 2025. 2026 stands at 1,092 through September.

Every month, in full

The raw counts behind the charts above, so you can check our arithmetic against City of Detroit Open Data — Improve Detroit Issues yourself.

Average share is the mean of each full calendar year’s monthly share, so a heavy year cannot dominate the seasonal curve. The 2026 column is incomplete by design.

The 25 busiest ZIP codes in Detroit

Totals cover 2023 through 2025, the three full calendar years in the window. Per square mile uses the Census ZCTA land area, which is what makes a small dense ZIP comparable to a large one.

30 ZIP codes recorded at least one complaint. Volume tracks reporting behaviour as well as rodent activity: a block that knows how to use 311 shows up more than an identical block that does not.

Freeze dates for Detroit

The nearest NOAA station publishing 1991–2020 first-freeze normals is DEARBORN #2, 4.4 miles from the city point. One autumn in ten sees its first 32°F night by October 10; a typical year gets one around October 25; nine years in ten have had one by November 7. The station averages 125.3 nights a year below freezing.

We went into this expecting complaints to climb toward the first freeze. In Detroit they do not. Detroit complaints peak in October, and by November the month carries 6.01 percentage points less of the year than September did, with the typical first freeze still landing in October. We publish the gap rather than smoothing it. The likeliest reason is that a 311 rodent complaint is mostly an outdoor rat report, and outdoor rat activity runs highest in warm weather, while the autumn move indoors is house mouse behaviour that rarely becomes a city service request. Somebody with mice behind a kitchen cabinet calls an exterminator, not the city.

What removal costs if it is your house

National 2026 planning ranges from our estimator, not Detroit quotes.

Frequently asked questions

Sources

• City of Detroit Open Data — Improve Detroit Issues — dataset improve_detroit, filtered on request_type='Rodent Extermination', extracted September 9, 2026.
• NOAA NCEI U.S. Climate Normals 1991–2020 — station USC00202016, DEARBORN #2.
• U.S. Census Bureau 2023 ZCTA gazetteer — ZIP land area used for the per-square-mile column.
• UC Statewide IPM Program — Pest Notes: Rats (Publication 74106) — rat behaviour and exclusion.