Costa Rica
Best Time to Dive in Guanacaste / Catalinas
10.55°N 85.82°W
Plan for December to April, when the downpours ease — 1 days a month of heavy rain instead of 11. The marine life holds steady all year, so the weather picks the month.
- Best time
- Dec–Apr
- Water
- 27–29 °C
- Visibility
- 5–25 m
- Dived from
- day boat
- Tidal range
- 1.4–2.5 m
- Species logged
- 9
Where it is
111 km across · coastline from Natural Earth 10m
Diving in Guanacaste / Catalinas — monthly breakdown
A year of scuba diving conditions at a glance. Hover a month to isolate it.
| January | February | March | April | May | June | July | August | September | October | November | December | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Conditions | Excellent | Excellent | Excellent | Excellent | Poor | Poor | Moderate | Moderate | Poor | Poor | Moderate | Excellent |
| Water temp (°C) | 28 | 27 | 28 | 29 | 29 | 29 | 29 | 29 | 29 | 29 | 28 | 28 |
| Visibility (m) | 10–20 | 5–15 | 5–15 | 10–20 | 15–25 | 15–25 | 10–20 | 15–25 | 15–25 | 10–20 | 10–20 | 10–20 |
| Marine life | Steady | Busy | Busy | Busy | Steady | Busy | Steady | Busy | Steady | Steady | Steady | Steady |
| Best time | Peak | Peak | Peak | Peak | Peak |
Excellent Good Moderate PoorPeak season Dec–Apr
Long-term averages, 2016–2025. Visibility is estimated from satellite chlorophyll-a. Water temperature is the surface mean; it is cooler at depth.
The Guanacaste / Catalinas diving season
May to June · Off season
2 monthsJFMAMJJASOND
- Water temperature
- 29–29 °C
- Visibility
- 15–25 m
- Rain
- 26 days a month
Diving conditionsThis is the wet season topside. The wind eases. The sea is rougher.
Marine lifeOceanic manta (hit-or-miss) peaks at Guanacaste / Catalinas in these months.
July to August · Shoulder season
2 monthsJFMAMJJASOND
- Water temperature
- 29–29 °C
- Visibility
- 10–20 m
- Rain
- 25 days a month
Diving conditionsExpect some swell. The wind eases. It rains more.
Marine lifeOceanic manta (hit-or-miss) peaks at Guanacaste / Catalinas in these months.
September to October · Off season
2 monthsJFMAMJJASOND
- Water temperature
- 29–29 °C
- Visibility
- 15–25 m
- Rain
- 29 days a month
Diving conditionsThe sea is rougher. It rains more.
November · Shoulder season
1 monthJFMAMJJASOND
- Water temperature
- 28–28 °C
- Visibility
- 10–20 m
- Rain
- 22 days a month
Diving conditionsThis is the wet season topside. The wind eases. The sea is rougher.
December to April · Peak season
5 monthsJFMAMJJASOND
- Water temperature
- 27–29 °C
- Visibility
- 10–20 m
- Rain
- 6 days a month
Diving conditionsThe wind is up. The sea is calmer.
Marine lifeMunk's mobula (hit-or-miss), Oceanic manta (hit-or-miss) peak at Guanacaste / Catalinas in these months.
- Spring tides run 2.5 m against 1.4 m on neaps, so currents build around the full and new moon.
- Water temperature is satellite sea-surface temperature, so expect it cooler below the thermocline.
- Visibility is estimated from satellite chlorophyll-a.
Guanacaste / Catalinas water temperature and weather
793 underwater observation records · 24 surveyed years of ocean data · 10 years of sea temperature
Water & weather
Guanacaste / Catalinas water temperature by month
The dashed line is the monthly average. Eight days in ten fall inside the band.
10th to 90th percentile rangemonthly mean
Rarely
rough enough to cancel
Seas top 1.5 m on 3% of days. Enough to cancel a day boat
0
blowy days a month
Gusts over 40 km/h, about where a day boat stays in port
18
wet days a month
7 of them bring heavy rain
| Month | Swell | Gusts over 40 km/h | Wet days | Heavy rain | Air | Daylight |
|---|---|---|---|---|---|---|
| January | 1.1 m | 0% | 4 | 0 | 32 °C | 11.4 h |
| February | 1.0 m | 1% | 2 | 0 | 33 °C | 11.7 h |
| March | 1.0 m | 0% | 4 | 0 | 34 °C | 11.9 h |
| April | 1.0 m | 0% | 12 | 2 | 33 °C | 12.2 h |
| May | 1.3 m | 0% | 25 | 10 | 31 °C | 12.5 h |
| June | 1.5 m | 0% | 28 | 14 | 30 °C | 12.6 h |
| July | 1.2 m | 0% | 23 | 8 | 31 °C | 12.6 h |
| August | 1.2 m | 0% | 26 | 11 | 30 °C | 12.3 h |
| September | 1.5 m | 0% | 29 | 13 | 30 °C | 12.1 h |
| October | 1.4 m | 0% | 30 | 17 | 29 °C | 11.8 h |
| November | 1.3 m | 0% | 22 | 7 | 29 °C | 11.5 h |
| December | 1.1 m | 0% | 7 | 1 | 31 °C | 11.4 h |
Swell is the rough end of the month: nine days in ten come in under it. Sea temperature covers 10 years, waves 4.
Pick your week
48 weeks from the daily record. Darker is better, against this site's own year. Pick a month for the detail.
| Week 1 | January week 1: Excellent | February week 1: Excellent | March week 1: Excellent | April week 1: Excellent | May week 1: Poor | June week 1: Poor | July week 1: Moderate | August week 1: Moderate | September week 1: Poor | October week 1: Poor | November week 1: Moderate | December week 1: Excellent |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Week 2 | January week 2: Excellent | February week 2: Excellent | March week 2: Excellent | April week 2: Excellent | May week 2: Poor | June week 2: Poor | July week 2: Moderate | August week 2: Moderate | September week 2: Poor | October week 2: Poor | November week 2: Moderate | December week 2: Excellent |
| Week 3 | January week 3: Excellent | February week 3: Excellent | March week 3: Excellent | April week 3: Excellent | May week 3: Poor | June week 3: Poor | July week 3: Moderate | August week 3: Moderate | September week 3: Poor | October week 3: Poor | November week 3: Moderate | December week 3: Excellent |
| Week 4 | January week 4: Excellent | February week 4: Excellent | March week 4: Excellent | April week 4: Good | May week 4: Poor | June week 4: Poor | July week 4: Moderate | August week 4: Moderate | September week 4: Poor | October week 4: Poor | November week 4: Moderate | December week 4: Excellent |
Excellent Good Moderate PoorBest week to go: first of April
January, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 28 °C | 1.1 m | 18 km/h | 20% |
| Week 2 | Excellent | 28 °C | 1.0 m | 20 km/h | 14% |
| Week 3 | Excellent | 28 °C | 1.1 m | 21 km/h | 11% |
| Week 4 | Excellent | 28 °C | 1.1 m | 23 km/h | 7% |
February, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 28 °C | 1.0 m | 24 km/h | 5% |
| Week 2 | Excellent | 27 °C | 1.0 m | 23 km/h | 6% |
| Week 3 | Excellent | 27 °C | 1.0 m | 24 km/h | 9% |
| Week 4 | Excellent | 27 °C | 1.0 m | 24 km/h | 7% |
March, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 27 °C | 1.0 m | 23 km/h | 6% |
| Week 2 | Excellent | 28 °C | 1.0 m | 22 km/h | 13% |
| Week 3 | Excellent | 28 °C | 1.0 m | 22 km/h | 17% |
| Week 4 | Excellent | 28 °C | 1.0 m | 22 km/h | 16% |
April, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 28 °C | 1.0 m | 21 km/h | 23% |
| Week 2 | Excellent | 29 °C | 1.0 m | 21 km/h | 33% |
| Week 3 | Excellent | 29 °C | 1.1 m | 20 km/h | 39% |
| Week 4 | Good | 29 °C | 1.1 m | 18 km/h | 53% |
May, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 29 °C | 1.1 m | 16 km/h | 66% |
| Week 2 | Poor | 29 °C | 1.1 m | 16 km/h | 72% |
| Week 3 | Poor | 29 °C | 1.3 m | 15 km/h | 82% |
| Week 4 | Poor | 29 °C | 1.3 m | 15 km/h | 91% |
June, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 29 °C | 1.4 m | 14 km/h | 96% |
| Week 2 | Poor | 29 °C | 1.6 m | 13 km/h | 97% |
| Week 3 | Poor | 29 °C | 1.6 m | 14 km/h | 92% |
| Week 4 | Poor | 29 °C | 1.4 m | 15 km/h | 85% |
July, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 29 °C | 1.3 m | 15 km/h | 82% |
| Week 2 | Moderate | 29 °C | 1.2 m | 16 km/h | 75% |
| Week 3 | Moderate | 29 °C | 1.2 m | 16 km/h | 68% |
| Week 4 | Moderate | 29 °C | 1.1 m | 15 km/h | 74% |
August, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 29 °C | 1.1 m | 15 km/h | 80% |
| Week 2 | Moderate | 29 °C | 1.1 m | 14 km/h | 85% |
| Week 3 | Moderate | 29 °C | 1.2 m | 14 km/h | 85% |
| Week 4 | Moderate | 29 °C | 1.3 m | 14 km/h | 88% |
September, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 29 °C | 1.2 m | 13 km/h | 94% |
| Week 2 | Poor | 29 °C | 1.4 m | 13 km/h | 96% |
| Week 3 | Poor | 29 °C | 1.5 m | 13 km/h | 96% |
| Week 4 | Poor | 29 °C | 1.7 m | 13 km/h | 96% |
October, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 29 °C | 1.7 m | 13 km/h | 96% |
| Week 2 | Poor | 29 °C | 1.5 m | 14 km/h | 98% |
| Week 3 | Poor | 29 °C | 1.4 m | 13 km/h | 96% |
| Week 4 | Poor | 28 °C | 1.4 m | 13 km/h | 93% |
November, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 28 °C | 1.4 m | 13 km/h | 85% |
| Week 2 | Moderate | 28 °C | 1.3 m | 14 km/h | 77% |
| Week 3 | Moderate | 28 °C | 1.3 m | 14 km/h | 72% |
| Week 4 | Moderate | 28 °C | 1.2 m | 14 km/h | 58% |
December, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 28 °C | 1.0 m | 16 km/h | 38% |
| Week 2 | Excellent | 28 °C | 1.0 m | 17 km/h | 26% |
| Week 3 | Excellent | 28 °C | 1.0 m | 18 km/h | 18% |
| Week 4 | Excellent | 28 °C | 1.1 m | 18 km/h | 19% |
10 years of daily records, averaged into weeks.
Gear & storms
What to wear
Off the coldest water of each month, not the average — that is what the suit has to cope with.
| January | February | March | April | May | June | July | August | September | October | November | December | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Suit | January: 3 mm | February: 3 mm | March: 3 mm | April: skin | May: skin | June: skin | July: skin | August: skin | September: skin | October: skin | November: skin | December: skin |
- Jan–Mar3 mm full suit
- Apr–Decskin or 3 mm shorty
Swell through the year
The rough end of each month — nine days in ten come in under it.
Amber is over 1.5 m.
Tides
Tropical storms
2 of the last 30 Julys saw a tropical storm pass within 250 km. Anything has been recorded May, Jul, Oct–Nov.
Share of the last 30 years with a storm that month.
- NOAASea surface temperature, from OISST and MUR
- ERA5Wind, waves, rain and air temperature, via Open-Meteo
- OBISMarine species records within 60 km
- IBTrACSTropical cyclone tracks, 1996 to 2025
Guanacaste / Catalinas marine life — what you'll see diving
| Species | When | Observed window | Reliability | Evidence | Records |
|---|---|---|---|---|---|
| Green turtle | Feb–Apr | Likely | 402 | ||
| Whitetip reef shark | All year | Likely | 46 | ||
| Hawksbill turtle | All year | Likely | 37 | ||
| Bigeye trevally | All year | Hit-or-miss | 25 | ||
| Munk's mobula | Mar | Hit-or-miss | 16 | ||
| Bottlenose dolphin | Sep | Hit-or-miss | 12 | ||
| Humpback whale | Jan, Mar, Aug | Near-guaranteed | 206 | ||
| Bull shark | Jan, May–Jun | Hit-or-miss | 12 | ||
| Oceanic manta | Mar, Jun, Aug | Hit-or-miss | 10 |
Peak Present
- Observed window
- Months with records. Peak is where most of them fall.
- Reliability
- Near-guaranteed in 60% of surveyed years or more
- Likely 30% to 60%
- Hit-or-miss under 30%
- Evidence
- Years it was seen, out of the years anyone surveyed.
- Records
- OBIS sightings within 60 km.
These are sightings people logged, not a full survey of the reef. A species missing from a month may just mean nobody recorded one.
Diving Guanacaste / Catalinas — common questions
- When is the best time to dive Guanacaste / Catalinas?
- Plan for December to April, when the downpours ease — 1 days a month of heavy rain instead of 11. The marine life holds steady all year, so the weather picks the month.
- When is the diving season in Guanacaste / Catalinas?
- The diving season in Guanacaste / Catalinas runs December to April.
- Is the diving in Guanacaste / Catalinas good for beginners?
- Yes. It suits Open Water divers, so it works for a first trip after certification.
- How warm is the water in Guanacaste / Catalinas?
- Between 27 and 29 °C at the surface across the year, coldest in February and warmest in May. It runs cooler below the thermocline.
- What wetsuit do I need in Guanacaste / Catalinas?
- A 3 mm full suit covers the coldest water of the year. In the warmest months a skin or 3 mm shorty is enough.
- What is the visibility like in Guanacaste / Catalinas?
- Roughly 5 to 25 m depending on the month. That is estimated from satellite chlorophyll-a rather than measured in the water.
- What will I see diving Guanacaste / Catalinas?
- The most consistently recorded species are Green turtle (likely), Whitetip reef shark (likely) and Hawksbill turtle (likely), from 793 records within 60 km.
- Does Guanacaste / Catalinas get tropical storms?
- Yes. Over 30 years of records a storm passed within 250 km in May, Jul, Oct–Nov, most often in July at 2 of 30 years.
- Is there current in Guanacaste / Catalinas?
- The tide rises and falls 2.5 m around the full and new moon, against 1.4 m in between. How much of that becomes current depends on the shape of the channel.
- When should I avoid Guanacaste / Catalinas?
- October is the weakest month for conditions.
- How do you dive Guanacaste / Catalinas?
- Mostly from day boats. Trips run through the season, Dec–Apr.