Mazatlán's winter is nearly mosquito-free. Sinaloa's dengue season ends late.

Are there mosquitoes in Mazatlán? A few, and not many in winter. Forum regulars tend to describe the dry months as nearly mosquito-free away from the marina and the estuaries, where tiny biting midges go for ankles at dusk. The day-biting dengue mosquito is the one with a health angle, and Sinaloa's season runs later into the fall than most of Mexico's. Our Mexico briefing covers the rest of the country, and the Cancún briefing covers the Caribbean coast.

Dengue in Sinaloa runs late

Dengue is endemic in Sinaloa. Mexico's health ministry counted 683 confirmed cases and 2 deaths in the state by October 19, 2026, against 930 cases and 6 deaths at the same point of 2025. The rate is still high by Mexican standards, at 21.29 confirmed cases per 100,000 people, sixth of 32 states and about three and a half times the national 5.99. The ministry's list of the highest-rate municipalities, led by Mocorito, El Fuerte and Choix, doesn't include Mazatlán in 2025 or 2026, and local press placed the city's early-2026 cases in residential neighborhoods rather than the hotel zone.

Timing is what sets Sinaloa apart. In 2025, more than half of the state's confirmed cases were added after mid-October, so much of each season comes in late fall, and its tail reaches into early December, especially after a wet fall. By February the dry season has taken over, and February to April is the quietest stretch of the year. For a winter trip, that makes the first weeks of December the time to be strictest with the daytime routine.

The rest of the list is short. Mexico's weekly bulletin recorded no chikungunya, Zika, West Nile or malaria in Sinaloa in 2026 through mid-October. The CDC lists malaria as "Rare in the states of Oaxaca, Sinaloa, Sonora, and Tabasco" and recommends bite precautions there, with no prevention medicine. It doesn't recommend the yellow fever vaccine for Mexico.

Where the bites are

In town, the biter is the day-flying Aedes mosquito, which tends to breed in water containers in the courtyards of Old Mazatlán and the residential neighborhoods. Beachfront hotels in the Golden Zone and along the Sábalo-Cerritos strip tend to get the onshore breeze, which helps. Forum posters tend to single out the marina and its canals, the estuaries (esteros), golf courses and vacant lots as places where mosquitoes linger, and at least one found them inside a Golden Zone apartment.

Many of the ankle bites visitors blame on "sand fleas" are no-see-ums, tiny biting midges, regulars say. They bite at dawn and dusk near still water, and a breeze grounds them. Our Barbados sand fly guide explains how they behave.

The routine is simple. Put repellent on over sunscreen in the morning before Old Mazatlán, the Malecón or Stone Island, again after swimming and again in the late afternoon. Cover ankles and calves for dinner near the marina or the estuaries. Choose an air-conditioned or well-screened room and keep balcony doors closed in the evening, especially in early December. Our dengue & Zika routine has the full schedule.

One item isn't about mosquitoes. Sinaloa reports spotted fever, the Rocky Mountain spotted fever group spread by dog ticks, every year, with 27 cases in 2026 through mid-October. The state isn't on the CDC's tick notice, which covers the northern border states, but its advice applies if you spend time in rural areas or around dogs. Use repellent, check for ticks daily and avoid contact with dogs.

Where you're going

Scores are for a December–April trip.

What travelers report

Paraphrased from a TripAdvisor forum thread and linked so you can read it in full. It isn't dated, and an unseasonal rain can bring biters back for a few days in any winter.

• Mazatlán · January

  A poster who wondered whether bites on an earlier trip came from sand fleas asked about January. Replies said mosquitoes are rare in Mazatlán in January; one added that even in the July to September rainy season only some areas have them, and another had only met mosquitoes there in summer. TripAdvisor ↗

One rule outlasts the trip. Any fever during the trip or within two weeks of returning means a doctor visit, and you tell the doctor you were in Sinaloa. That detail gets you the right tests quickly.

Traveler questions