What City 311 Data Says About Rodent Season
By Marcus Ellery, Pest Control Editor · Updated September 2026 · Methodology
Six cities publish rodent complaints as open data, and we pulled all of them for 2023 through 2026: 104,098 complaints in 2025 across the six. What that lets us show is when each city’s own complaints peak and which parts of it generate the most. What it does not let us show is which city has the worst rat problem, because each of these six counts a different event. Comparing the levels would compare reporting systems, so every number here stays inside its own city.
6
Cities
2023–2026
Years pulled
104,098
Complaints in 2025
5 of 6
Peak in summer
The shape of the year, city by city
Each line is one city’s share of its own annual complaints, month by month, averaged over the full calendar years in the window. An average month would sit at 8.3%. Levels are deliberately absent: this chart answers when, never how many.
Peak, trough, and trend
| City | Peak month | Quietest month | 2025 total | 2023–2025 |
|---|---|---|---|---|
| New York City, NY NYC Open Data — 311 Service Requests (2010 to Present) | July10.86% of the year | December | 31,312 | -25%down |
| Chicago, IL Chicago Data Portal — 311 Service Requests | July12.29% of the year | December | 43,083 | -8.6%down |
| Boston, MA Analyze Boston — 311 Service Requests | August13.45% of the year | February | 5,220 | +33.4%up |
| Washington, DC Open Data DC — 311 City Service Requests | June10.78% of the year | December | 16,685 | -6.4%down |
| Baltimore, MD Open Baltimore — 311 Customer Service Requests | August11.63% of the year | December | 6,020 | -18.5%down |
| Detroit, MI City of Detroit Open Data — Improve Detroit Issues | October12.37% of the year | December | 1,778 | -10.8%down |
Totals sit in the same column but are not comparable across rows. Each city’s definition is on its own page and in the card below.
What each city counts
New York City, NY
Every 311 service request filed under complaint type "Rodent", which covers resident-reported rat and mouse sightings, signs of rodents, and conditions attracting rodents. These are reports from the public, not confirmed infestations.
- Peak month
- July
- Geography published
- ZIP code (100% filled)
- Typical first freeze
- November 19 at NY AVE V BROOKLYN
Chicago, IL
Every 311 service request of type "Rodent Baiting/Rat Complaint", which is a request for the city to bait a location for rats. Chicago flags service requests it later merges into an existing one; those duplicates are excluded here so a single location counted once.
- Peak month
- July
- Geography published
- Ward (99.9% filled)
- Typical first freeze
- November 5 at CHICAGO NORTHERLY IS
Boston, MA
Every Boston 311 case titled "Rodent Activity", the case type the Inspectional Services Department opens when a resident reports rats or mice at an address.
- Peak month
- August
- Geography published
- ZIP code (70.1% filled)
- Typical first freeze
- November 9 at BOSTON LOGAN INTL AP
Washington, DC
Every 311 service request DC Health opens to inspect and bait a property for rats. It is a request for city treatment, not a confirmed sighting. DC renamed the category from "Rodent Inspection and Treatment" to "DC Health Rodent & Vector Control" during 2026, so both codes are counted and the series runs continuously across the rename.
- Peak month
- June
- Geography published
- ZIP code (100% filled)
- Typical first freeze
- November 8 at NATL ARBORETUM DC
Baltimore, MD
Resident-initiated requests for city action on rats: Baltimore’s "SW-Rat Rubout" and follow-up requests plus Housing’s "HCD-Rodents" requests. Baltimore also logs a much larger volume of "SW-Rat Rubout Proactive" records, which are baiting runs the Department of Public Works schedules itself rather than anything a resident reported. Those are excluded here, because counting them would make the city’s work calendar look like rodent activity.
- Peak month
- August
- Geography published
- ZIP code (100% filled)
- Typical first freeze
- November 21 at MD SCI CTR BALTIMORE
Detroit, MI
Every Improve Detroit request of type "Rodent Extermination", the request residents file to have the city treat a property for rats or mice.
- Peak month
- October
- Geography published
- ZIP code (98.2% filled)
- Typical first freeze
- October 25 at DEARBORN #2
Find your own window
Most people do not live in one of these six cities. The freeze layer covers the whole country, so a ZIP code gets you the dates even where no 311 data exists.
Frequently asked questions
What state has the worst rodent problem?
Nobody can answer that from open data, and we are not going to pretend otherwise. There is no national rodent survey. What exists is 311 complaint data from individual cities, and every city counts a different event: New York logs a resident-reported sighting, Chicago logs a request for baiting, Baltimore logs a Rat Rubout work order. Complaint volume also tracks how well a city advertises its 311 line. Ranking states or cities on those numbers would be a ranking of reporting systems.
So what can 311 data actually tell me?
Two things it is genuinely good at. First, when a city’s own rodent complaints peak, because the reporting system is the same all year, so the shape of the year is honest even when the level is not comparable to anywhere else. Second, which parts of that one city generate the most complaints, which is useful if you live there.
Why are the counts so different between cities?
Because the definitions are. Look at any two rows: New York City counts 31,312 in 2025 under one definition and Detroit counts 1,778 under another. Population differs, the 311 systems differ, and the thing being recorded differs. Read each city page for the exact filter we used.
Do complaints climb toward winter?
No, and this surprised us. We built this layer expecting a September to November climb toward the first freeze, because that is what every rodent-season article says. The data says the opposite in all 6 cities: 5 peak in summer, and in every single one November carries a smaller share of the year than September does. The likeliest explanation is that a 311 rodent complaint is largely an outdoor rat report, and outdoor rat activity peaks in warm weather. The autumn move indoors is house mouse behaviour, and people with mice call an exterminator rather than the city. We left the finding as we found it.
Does a rising trend mean more rats?
Not on its own. A city that promotes its 311 app, adds a category, or runs an abatement campaign will see the count move without the rodent population moving. We publish the direction and the definition and let you judge. Where a city changed systems mid-window we say so rather than splicing the series.
How current is this?
The window runs from January 2023 through the current year to date. 2025 is the most recent complete calendar year, and every count for 2026 is partial and labelled as such. The extract was taken on September 9, 2026.
Sources
- NYC Open Data — 311 Service Requests (2010 to Present) — dataset erm2-nwe9, filtered on
complaint_type='Rodent'. - Chicago Data Portal — 311 Service Requests — dataset v6vf-nfxy, filtered on
sr_type='Rodent Baiting/Rat Complaint' AND duplicate=false. - Analyze Boston — 311 Service Requests — dataset 311-service-requests, filtered on
case_title ILIKE '%Rodent Activity%'. - Open Data DC — 311 City Service Requests — dataset DCGIS_DATA/ServiceRequests, filtered on
SERVICECODEDESCRIPTION IN ('Rodent Inspection and Treatment','DC Health Rodent & Vector Control'). - Open Baltimore — 311 Customer Service Requests — dataset 311_Customer_Service_Requests, filtered on
SRType IN ('SW-Rat Rubout','SW-Rat Rubout Follow-up','SW-Rat Rubout Alley Concern (SW creation only)','HCD-Rodents') [excludes SW-Rat Rubout Proactive]. - City of Detroit Open Data — Improve Detroit Issues — dataset improve_detroit, filtered on
request_type='Rodent Extermination'.
PestCost is an independent cost-information site, not a pest-control company. We publish no reviews, no star ratings, and no city rankings. Complaint counts are records of what residents reported to a city, not a census of rodents.