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Baltimore Mosquito Forecast

Today's mosquito activity in Baltimore, the week ahead, and what to do about it. Updated hourly.

Bite Index · Sunday, November 8

Low

Mosquito activity in Baltimore is low today.

Few mosquitoes. You may see one or two at dusk near water.

About normal for November in Baltimore City.

  • Off-season: even with rain and warmth, populations are a fraction of summer's.
  • Tonight: a cool 50°F evening, light wind — poor flying weather, so fewer bites than the population alone would suggest.
  • 0.8 in. of rain Oct 14–Oct 28 is now producing adults (cool weather slowed the hatch, so the window is longer than usual).

The week ahead

Each day's Bite Index, from this week's weather and the rain that is still hatching. Forecast days get less certain as the week goes on.

  1. Today
    5Low62°/43°dry
  2. Mon
    5Low59°/43°dry
  3. Tue
    6Low67°/41°dry
  4. Wed
    6Low67°/52°dry
  5. Thu
    4Low62°/53°0.2 in
  6. Fri
    3Low55°/46°0.4 in
  7. Sat
    3Low47°/40°0.3 in

Protect tonight

You can probably skip repellent tonight.

  1. If you're near a creek, pond or heavy shade at dusk, a light application on ankles and arms is plenty.
  2. Good night to tip out any containers holding water; what you empty now won't hatch next week.
Which repellent, and how much: DEET vs picaridinBest natural repellents

Why Baltimore's mosquitoes do what they do

Baltimore wraps around the Patapsco's tidal harbor, with Gwynns Falls and the Jones Falls running through the city and humid summers that favor both the daytime-biting Asian tiger mosquito and the Culex of the storm drains. Maryland's Department of Agriculture runs mosquito control for the city and posts spray-night notices by neighborhood.

  • Tidal harbor and streams: the Inner Harbor, Middle Branch and the Jones Falls hold standing water.
  • Rowhouse neighborhoods: alleys, drains and backyards breed Asian tiger mosquitoes and Culex.
  • Humid summers: July and August dusk conditions are ideal for flight.
  • Short season: June through September.

A typical year in Baltimore City

The long-run mosquito index by month from our season map (NOAA climate normals plus effort-corrected sightings). Today's Bite Index is the live version of this; the month you're in is marked.

  1. JJanuary: 0
  2. FFebruary: 0
  3. MMarch: 0
  4. AApril: 16
  5. MMay: 45
  6. JJune: 71
  7. JJuly: 89
  8. AAugust: 91
  9. SSeptember: 78
  10. OOctober: 48
  11. NNovember: 0
  12. DDecember: 0

Local surveillance and West Nile virus

The Bite Index measures nuisance biting, not disease. Baltimore City's health department traps and tests mosquitoes through the season and publishes positive West Nile pools by ZIP code. When your ZIP has an active advisory, follow it regardless of today's number.

How the Bite Index is scored

The index is a model of conditions, not a mosquito count. Four weather factors are combined on a 0–100 scale, then scaled by the season. Every factor and today's value for it is listed here so you can check the number yourself. It uses the same temperature curve and rain logic as our county-level mosquito season map, which has been validated against effort-corrected sighting data across 41 states.

BBreeding pressure

Rain 7–14 days ago (0.8 in. between Oct 14 and Oct 28). Eggs need water to hatch, and at summer temperatures the egg-to-biting-adult cycle takes about a week, so today's mosquitoes are last week's rain. Cool weather stretches the window; hot dry days shrink it as shallow water evaporates.

Weight 40%
Today 43%

DDevelopment

The trailing two-week average temperature, on the same curve as our national season map: nothing below 50°F, full speed at 78–88°F, a small penalty in extreme heat.

Weight 25%
Today 26%

ATonight's activity

Whether the population that exists will actually fly and bite this evening: dusk temperature (65–85°F is ideal), wind (they stop flying around 10 mph), humidity, and rain around sunset.

Weight 25%
Today 0%

GGround truth

A nudge from local trap counts and reports when we have them. For Baltimore this is neutral today; the health department's surveillance is linked above and will feed this factor as we wire it in.

Weight 10%
Today neutral

SSeason gate

A multiplier from the calendar: fully open in the city's season months, half-open in the shoulder months, nearly closed in deep winter unless the week is warm. Below a 50°F weekly average the index is simply 0.

Weight ×
Today 15%

index = 100 × S × (0.40 × (0.2 + 0.8·B) + 0.25 × D + 0.25 × A + 0.10 × (0.5 + 0.5·G))

Bands: Low 0–20 · Moderate 21–40 · High 41–60 · Very High 61–80 · Severe 81–100. Weather is from Open-Meteo (observations and the 7-day forecast), refreshed hourly. The lag and temperature thresholds follow published work on Culex and Aedes development (Rueda et al. 1990; Cornell NRCC degree-day emergence; JAMCA 2024 on rainfall two to four weeks before trap peaks).

Questions people ask about mosquitoes in Baltimore

When is mosquito season in Baltimore?
June through September, peaking in July and August. The first frost, usually late October, ends it.
Why do I get bitten in the daytime in Baltimore?
The Asian tiger mosquito breeds in small containers in rowhouse yards and alleys and bites by day. It is the city's dominant nuisance species; Culex take over at dusk.
Is West Nile virus a risk in Baltimore?
Yes. The state detects West Nile in city mosquitoes most summers and schedules spray nights in response. Those notices are authoritative; follow them over the index.
Where does this forecast's data come from?
Open-Meteo weather for downtown Baltimore, scored by our documented model and compared with the city's season-map climatology. Not a trap count.

Also covers Towson, Columbia, Dundalk, Catonsville, Glen Burnie, Essex, Patterson Park, Druid Hill Park: the forecast point is central Baltimore, and conditions within about 30 miles track it closely. Weather fetched Nov 8, 12:28 PM local time.

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