The short answer
For the best mix of weather, sea conditions and value, come between late February and early April or from late May to June. December to February has the most comfortable air but the highest prices; July to November is wetter and carries the typhoon risk, with good deals outside the school holidays.
Temperatures hardly move: days of about 29–31 °C and nights of about 24–25 °C all year, with sea temperatures of roughly 27–30 °C. Guam, at the southern end of the chain, is slightly wetter than Saipan; the uninhabited northern islands are a little cooler in winter.
Dry season and wet season
Islanders speak of two seasons. The dry season (fanumnangan), from about December to June, brings steady north-easterly trade winds, lower humidity and passing showers. The wet season (fanuchånan), from about July to November, is hotter and stickier, with slack winds, heavy downpours — often in the afternoon or overnight — and occasional days of continuous rain when a tropical system passes. Even then, mornings are frequently bright and the lagoons stay swimmable.
Month by month
A general guide for Guam and Saipan. Rainfall averages are in each destination’s own when-to-go page.
| Month | Weather | Sea | Crowds and prices |
|---|---|---|---|
| January | Dry, breezy, comfortable | Windward coasts rough; lagoons calm | Peak: New Year, then Lunar New Year (late Jan or Feb) |
| February | Driest period begins | As January | High; quieter after Lunar New Year |
| March | Dry and sunny | Good; winds easing | Moderate — a sweet spot |
| April | Dry, warming up | Often the clearest water | Moderate, rising for Golden Week at month end |
| May | Mostly dry; first heavy showers | Calm and clear | Busy in the first week, then quiet |
| June | Transition; more humid | Calm; good diving | Quiet — good value |
| July | Wet season starts | Calm between squalls | Busy: school holidays; local Liberation Day festivities |
| August | Wettest month | Variable; storm swell possible | Busy until late August |
| September | Wet; peak typhoon period | Variable | Quiet and cheap, except around Chuseok |
| October | Wet; typhoons still possible | Variable | Quiet |
| November | Rain easing | Improving | Quiet — good value |
| December | Trade winds return | Windward coasts roughen | Rising to the Christmas–New Year peak |
Typhoons
The Marianas lie in the most active tropical-cyclone basin on Earth. Typhoons can form in any month but are most likely from about August to November. In most years none makes a direct hit on a given island; when one does, the effects are severe — Super Typhoon Yutu devastated Saipan and Tinian in October 2018, and Typhoon Mawar struck Guam in May 2023.
Buildings are designed for this, forecasts give several days’ warning, and hotels have well-rehearsed procedures. For visitors the realistic consequences are cancelled flights, a day or two indoors and closed attractions afterwards. In the wet season, buy changeable tickets and insurance that covers weather disruption, and follow the US National Weather Service office on Guam for official advisories.
Festivals and events
Dates move from year to year; check locally. Every village also holds a patron-saint fiesta at some point in the year.
- February: Tinian’s Hot Pepper Festival has usually been held around mid-month.
- March: Guam History and Chamorro Heritage Day in early March, marked at Umatac; Mes CHamoru, Chamorro Month, all month on Guam.
- April: an international marathon on Guam; Saipan’s Flame Tree Arts Festival has often been held in spring.
- May: Taste of the Marianas food festival on Saipan, traditionally on Saturday evenings.
- Late spring–early summer: the Guam Micronesia Island Fair; flame trees in bloom on Saipan.
- July: CNMI Liberation Day on 4 July on Saipan; Guam Liberation Day on 21 July, the island’s biggest celebration.
- October: the fiesta of San Francisco de Borja on Rota.
- December: Santa Marian Kamalen procession in Hagåtña on 8 December; Christmas illuminations in Tumon and Garapan.
Best time for…
- Beach and family holidays: any time; December to June for the most reliable sunshine.
- Diving and snorkelling: March to June for the calmest seas and clearest water, though you can dive all year. See the diving guide.
- Hiking: the dry season, starting early in the day.
- Low prices: June, and September to mid-December, outside Korean and Japanese holidays.
- Island-hopping by small plane: the dry season, when weather cancellations are fewer. See getting there.