Costa Rica Sea Temperature by Month: Pacific and Caribbean, from NOAA's Satellite Record
Verified on 25 September 2026, against NOAA Coral Reef Watch’s own time-series files for its two mainland-coast Costa Rica stations (daily data from 1 January 1985 to 23 September 2026), the station outlines NOAA publishes, and NOAA’s methodology pages.
On NOAA’s monthly averages, Costa Rica’s Pacific water ranges from 27.7086 °C in October to 28.7900 °C in May (about 81.9–83.8 °F), and its Caribbean water from 26.8592 °C in February to 28.3900 °C in September (about 80.3–83.1 °F). Those are NOAA’s monthly-mean climatology for its “Costa Rica Pacific” and “Costa Rica Atlantic” satellite stations — night-time surface temperature calibrated to 0.2 m depth. Two cautions come with them: the averages are anchored to a 1985–1993 baseline, and in the ten years 2016–2025 the Caribbean station’s coolest daily reading averaged above that baseline in every month; and the Pacific number is one figure for four separate stretches of coast between 7.8 °N and 11.25 °N that, in our point tests, take in Golfito, Manuel Antonio, Montezuma and Tamarindo together.
The data describes two coasts with narrow seasonal swings in NOAA’s climatology — about 1.08 °C on the Pacific and 1.53 °C on the Caribbean (our arithmetic) — that peak in different months: the Pacific in May, the Caribbean in September.
Monthly averages, both coasts
NOAA’s “Averaged Monthly Mean” for each station, as published; the °F columns are our conversion.
| Month | Pacific °C | Pacific °F | Caribbean °C | Caribbean °F |
|---|---|---|---|---|
| January | 27.9493 | 82.3 | 27.0137 | 80.6 |
| February | 28.0827 | 82.5 | 26.8592 | 80.3 |
| March | 28.3914 | 83.1 | 27.2612 | 81.1 |
| April | 28.7470 | 83.7 | 27.7751 | 82.0 |
| May | 28.7900 | 83.8 | 28.3778 | 83.1 |
| June | 28.4607 | 83.2 | 28.2768 | 82.9 |
| July | 28.4016 | 83.1 | 27.8477 | 82.1 |
| August | 28.2038 | 82.8 | 27.9610 | 82.3 |
| September | 28.0841 | 82.6 | 28.3900 | 83.1 |
| October | 27.7086 | 81.9 | 28.3822 | 83.1 |
| November | 27.7602 | 82.0 | 28.0127 | 82.4 |
| December | 27.9019 | 82.2 | 27.5049 | 81.5 |
The Pacific’s warmest average month (May) is also the station’s published “Averaged Maximum Monthly Mean”, 28.7900 °C; the Caribbean’s is September, 28.3900 °C. The Pacific average is the warmer of the two from December to August; the Caribbean’s is the warmer in September, October and November (our comparison of the table).
Exactly what stretch of water each number covers
NOAA’s files state a single “Polygon Middle” point for each station — 9.5000 N, 84.4250 W for the Pacific and 9.9000 N, 82.8500 W for the Atlantic. That point is the middle of the outline, not the area measured. The outlines themselves, from the polygon layer NOAA’s station map loads, are:
| Station | Shape | Extent (our reading of NOAA’s vertices) |
|---|---|---|
| Costa Rica Pacific | four separate parts | (1) 7.800–9.650 N, 82.650–84.400 W · (2) 9.500–10.000 N, 84.650–85.200 W · (3) 9.650–10.100 N, 85.300–85.750 W · (4) 10.150–11.250 N, 85.400–86.200 W |
| Costa Rica Atlantic | one part | 9.400–10.250 N, 82.450–83.300 W |
NOAA builds each outline from its global 5 km reef-pixel mask plus a 20 km buffer, so a station covers the reef areas it was drawn around, not the whole coast.
We tested reference points against those outlines. Place coordinates are Wikipedia’s (a single point per town or park, not its shoreline), and the inside/outside result is our arithmetic:
| Place | Station it falls inside |
|---|---|
| Tamarindo, Las Baulas Marine National Park, Santa Rosa National Park | Pacific, part 4 |
| Montezuma | Pacific, part 2 |
| Quepos, Manuel Antonio National Park, Golfito, Corcovado National Park | Pacific, part 1 |
| Limón, Cahuita National Park | Atlantic |
| Jacó | neither — about 14 km outside Pacific part 2 |
| Ostional, Cabo Blanco | neither |
| Tortuguero | neither — about 54 km outside the Atlantic outline |
So read the Pacific column as one number for Tamarindo, Montezuma, Manuel Antonio and Golfito’s waters together. It cannot tell you whether Tamarindo’s water differs from Manuel Antonio’s, and it should not be quoted as a figure for either. The Caribbean column takes in Limón and Cahuita National Park in our tests; nothing on this page covers Tortuguero.
The spread inside each station, 2016–2025
NOAA’s daily files do not publish a regional average. They publish, for each day, the coolest pixel and the warmest pixel inside the outline. Averaging those two across every day of each month in 2016–2025 (283 to 310 days per month) gives the range below. All of it is our arithmetic on NOAA’s daily values.
| Month | Pacific: avg coolest – warmest pixel, °C | Caribbean: avg coolest – warmest pixel, °C |
|---|---|---|
| January | 25.85 – 29.47 | 27.39 – 27.70 |
| February | 25.19 – 29.98 | 27.35 – 27.61 |
| March | 25.38 – 30.28 | 27.72 – 28.02 |
| April | 26.94 – 30.29 | 28.20 – 28.57 |
| May | 28.58 – 29.93 | 28.92 – 29.29 |
| June | 28.51 – 29.49 | 29.00 – 29.32 |
| July | 28.07 – 29.33 | 28.33 – 28.64 |
| August | 28.35 – 29.42 | 28.81 – 29.11 |
| September | 28.40 – 29.34 | 29.26 – 29.55 |
| October | 27.90 – 28.91 | 29.21 – 29.57 |
| November | 27.14 – 28.47 | 28.59 – 28.98 |
| December | 26.31 – 28.87 | 27.65 – 28.04 |
Two things stand out in the numbers:
- The Pacific station is far from uniform from December to April. Its average gap between coolest and warmest pixel widens to about 4.8 °C in February and 4.9 °C in March, against under 1.4 °C from May to November. The single coolest daily reading in the decade was 21.45 °C, in February. NOAA’s file gives the value, not the location, so we cannot say which of the four parts it came from.
- The Caribbean station is nearly uniform all year — an average gap of 0.26 to 0.39 °C in every month.
Why the recent numbers sit above the monthly averages
NOAA’s methodology states that its monthly-mean climatologies use 28 years of satellite data (1985–2012) but are pinned to a baseline of 1985–1990 plus 1993. The monthly table at the top therefore describes the water around that baseline, by design — it is the yardstick NOAA measures heat stress against, not a forecast.
The recent record runs above it. On the Caribbean station, the 2016–2025 average of the daily coolest pixel is higher than NOAA’s monthly mean in all twelve months — in September, for example, 29.26 °C against 28.3900 °C (our comparison). On the Pacific station the coolest-pixel average is above the monthly mean only in June, August, September and October; in the other eight months it is below it (our comparison).
The latest reading: 23 September 2026
The most recent day in both files when we read them on 25 September 2026:
| Station | Coolest pixel | Warmest pixel | NOAA’s alert label |
|---|---|---|---|
| Costa Rica Pacific | 29.56 °C | 30.48 °C | Bleaching Alert Level 2 |
| Costa Rica Atlantic | 28.99 °C | 29.41 °C | Bleaching Watch |
NOAA’s station listing labels the Pacific station “Bleaching Alert Level 2” and the Atlantic “Bleaching Watch”. NOAA notes that its station pages still use its older alert scale, which stopped at Alert Level 2; the current scale runs to Level 5. The Pacific file’s anomaly column reads +2.4667 °C that day — NOAA’s figure for the pixel holding the station’s 90th-percentile HotSpot, measured against its daily climatology.
Air temperature and rainfall by region — a different dataset, from the national meteorological service — are on our best time to visit Costa Rica page.
What NOAA doesn’t publish
These are gaps in NOAA’s published files, checked on 25 September 2026:
- A town-level or beach-level sea temperature for Costa Rica. Both mainland-coast stations are regional; neither is a single-pixel station. NOAA’s listing has a third Costa Rica station, Isla del Coco, whose outline (5.30–5.80 N, 86.80–87.35 W, our reading of NOAA’s vertices) surrounds the offshore island, not the mainland coast.
- A daily regional average. Each day’s file row gives the coolest pixel, the warmest pixel and the 90th-percentile pixel only.
- Where inside the outline the coolest or warmest pixel was on a given day.
- Any station covering Tortuguero or the Caribbean coast north of the Atlantic outline.
How we researched this
Scope: this page reports source research on NOAA’s published data, not in-water measurements. On 25 September 2026 we downloaded NOAA Coral Reef Watch’s time-series files for its “Costa Rica Pacific” and “Costa Rica Atlantic” Regional Virtual Stations, the polygon layer its station map loads, the Regional Virtual Station product description, the station gauge pages, the 5 km methodology page and the all-stations listing. The monthly averages and the 23 September values are NOAA’s as published. The polygon extents, the place tests, the °F conversions, the 2016–2025 monthly ranges and every comparison between them are our arithmetic on those files. Place coordinates for the place tests come from Wikipedia’s coordinate service.
Last verified: 25 September 2026. NOAA adds a row to each file every day; the monthly averages change only if NOAA revises its climatology.
Figures on this page labelled our arithmetic, our conversion, our comparison or our reading are calculated by us from the sourced inputs cited below. Every other figure is reproduced as NOAA published it.
Sources
- NOAA Coral Reef Watch — Costa Rica Pacific time series (text file) — the Pacific monthly means, the 28.7900 °C maximum monthly mean, the polygon middle point, and every daily coolest-pixel, warmest-pixel and anomaly value, including 23 September 2026.
- NOAA Coral Reef Watch — Costa Rica Atlantic time series (text file) — the same for the Caribbean station, including the 28.3900 °C maximum monthly mean.
- NOAA Coral Reef Watch — station polygon layer (JSON) — the four-part Pacific outline, the one-part Atlantic outline and the Isla del Coco outline.
- NOAA Coral Reef Watch — Costa Rica Pacific gauge page — the SST trace taken where the HotSpot equals the station’s 90th-percentile HotSpot.
- NOAA Coral Reef Watch — Regional Virtual Stations — the reef-pixel mask with its 20 km buffer.
- NOAA Coral Reef Watch — 5 km product methodology — night-time SST calibrated to 0.2 m depth, and the 1985–2012 climatology on a 1985–1990 plus 1993 baseline.
- NOAA Coral Reef Watch — all stations and products — the “Bleaching Alert Level 2” and “Bleaching Watch” labels, the heritage-versus-current alert-scale note, and the third station, Isla del Coco.
- Wikipedia coordinate service — towns and parks — the reference points used in the place tests.
Written by Estuardo Enriquez. This site is independent, has no relationship with NOAA or any agency named here, and is not connected to any previous owner of this domain.