Updated October 2026
Castillo de San Marcos National Monument Weather by Month
Castillo de San Marcos National Monument is warmest in July, when the nearest NOAA climate station averages a high of 91°F and a low of 74°F, and coldest in January, with an average high of 68°F and an average low of 48°F. August and September are the wettest months, with about 7.2 inches of precipitation each.
These figures are NOAA's 1991–2020 climate normals, the 30-year average for each calendar month, from the nearest long-record weather station, 1.5 miles from the park's reference point. A single station cannot describe a whole park: temperatures elsewhere in Castillo de San Marcos National Monument can differ from these, particularly with elevation.
Warmest month
Jul
91°F avg high
Coldest month
Jan
48°F avg low
Longest days
Jun
13.9 h of daylight
Average weather at Castillo de San Marcos by month
| Month | Avg high | Avg low | Precipitation | Daylight |
|---|---|---|---|---|
| January | 68°F | 48°F | 2.7 in | 10.3 h |
| February | 70°F | 50°F | 2.7 in | 11.0 h |
| March | 74°F | 55°F | 3.4 in | 11.8 h |
| April | 80°F | 61°F | 2.9 in | 12.7 h |
| May | 85°F | 67°F | 3.7 in | 13.5 h |
| June | 89°F | 72°F | 6.3 in | 13.9 h |
| July | 91°F | 74°F | 4.9 in | 13.7 h |
| August | 90°F | 74°F | 7.2 in | 13.1 h |
| September | 87°F | 73°F | 7.2 in | 12.2 h |
| October | 82°F | 67°F | 4.4 in | 11.3 h |
| November | 75°F | 58°F | 2.3 in | 10.5 h |
| December | 69°F | 51°F | 3.0 in | 10.1 h |
| Year total | 50.7 in |
NOAA 1991–2020 climate normals from station USC00087826, 1.5 miles from the park's reference point. The station's snowfall normal is zero in all twelve months. Daylight is the monthly average, computed from the park's latitude. Each month links to how crowded Castillo de San Marcos is at that time of year.
Castillo de San Marcos weather by season
Winter: December to February
Average highs hold near 69°F in all three months, with average lows between 48°F and 51°F. Together the three months average 8.4 inches of precipitation, about 17% of the yearly total and less than in any other season. Daylight is at its shortest, about 10.1 hours in December.
Spring: March to May
Average highs climb from 74°F in March to 85°F in May, with average lows between 55°F and 67°F. Together the three months average 10 inches of precipitation, about 20% of the yearly total. Daylight lengthens from about 11.8 hours in March to 13.5 in May.
Summer: June to August
Average highs hold near 90°F in all three months, with average lows near 73°F. The average high is 90°F or hotter in July and August. Together the three months average 18.4 inches of precipitation, about 36% of the yearly total and more than in any other season. Daylight is at its longest, about 13.9 hours in June.
Fall: September to November
Average highs fall from 87°F in September to 75°F in November, with average lows between 58°F and 73°F. Together the three months average 13.9 inches of precipitation, about 27% of the yearly total. Daylight shortens from about 12.2 hours in September to 10.5 in November.
What the National Park Service says about the weather
St. Augustine has a semi-tropical climate with over 300 days of sunshine each year. Summers (May-September) are hot, bright, and humid with afternoon thunderstorms common. Temperatures range from the lower 70s to the mid 90s F. Spring (March-mid-May) and Autumn (October-late November) can be pleasant with temperatures ranging from the upper 50s into the 80s F. The Winter months (December-March) are usually dry. Temperatures can be cool ranging from the upper 30s through the 60sF.
Weather description courtesy of the National Park Service — official park site.
Today's forecast for Castillo de San Marcos
Averages describe a typical month, not this week. For current conditions and the seven-day outlook, the National Weather Service issues a forecast for the park's reference point at 29.90°N, 81.31°W. It covers that one spot, so other elevations in the park can differ from it, as they do from the averages above.
National Weather Service forecast for Castillo de San Marcos National Monument →
Weather and crowds together
July, the warmest month, sees about 1.2× the visitors of the park's average month. March is the busiest month of the year and September the quietest. To see those crowds set against the weather for all twelve months, read the best time to visit Castillo de San Marcos National Monument. For hotels, cabins and rentals close to the park, see where to stay near Castillo de San Marcos.
Where to stay near Castillo de San Marcos
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Top-rated places to stay near Castillo de San Marcos
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Frequently Asked Questions
July is the warmest month at Castillo de San Marcos National Monument, with an average high of 91°F and an average low of 74°F. That is the 1991–2020 average at the nearest long-record NOAA station, 1.5 miles from the park's reference point. Temperatures inside the park can differ, particularly with elevation.
January is the coldest month at Castillo de San Marcos National Monument, with an average low of 48°F and an average high of 68°F, based on NOAA 1991–2020 climate normals.
August and September are the wettest months, with about 7.2 inches of precipitation each. November is the driest, at about 2.3 inches. The station records about 50.7 inches of precipitation in an average year.
The nearest long-record NOAA station, 1.5 miles from the park's reference point, shows no measurable snowfall in any month of its 1991–2020 normals.
Weather at nearby parks
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Keep exploring
Sources: NOAA NCEI U.S. Climate Normals 1991–2020 (station USC00087826), daylight computed from latitude, weather description from the National Park Service, crowd levels from National Park Service Visitor Use Statistics (1979–2025). Updated 2026-10-11. Lodging results are provided by Stay22; WhenToVisitParks may earn a commission from bookings, at no extra cost to you.