Castle Island Weather Forecast

    • 48
    • 64

    Becoming Sunny

    • 52
    • 65

    Partly Sunny

    • 49
    • 63

    Rain Showers Likely

    • 50
    • 59

    Rain Showers Likely

    • 53
    • 68

    Chance Rain Showers

    • 56
    • 74

    Partly Sunny

Today 21 May Suffolk

Mostly cloudy. Much cooler with Highs in the mid 60s. North Winds 5 to 10 Mph, becoming northeast in the afternoon.

Tonight 21 May Suffolk

Mostly cloudy. Cooler with Lows in the upper 50s. North Winds 5 to 10 Mph.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Castle Island Temperature Statistics

May Temperature

Boston, Logan International Airport (1.2 miles)

  • Lowest 9 May, 2026

    42.7 °F

  • Average May

    58.8 °F

  • Highest 17 May, 2026

    90.6 °F

Climate (2021–Present)

Boston, Logan International Airport (1.2 miles)

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  • Average Low 2021–2026

    46.7 °F

  • Average 2021–2026

    53.6 °F

  • Average High 2021–2026

    60.9 °F
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