USA
Best Time to Dive in Alaska
57.06°N 135.36°W
You come for Sitka's cold-water walls, kelp and Steller sea lions. That does not change through the year, so go when the weather is best: May to August.
- Best time
- May–Aug
- Water
- 6–14 °C
- Visibility
- 0–15 m
- Dived from
- day boat
- Tidal range
- 2.2–4.0 m
- Species logged
- 7
Worth knowing: water around 6 °C.
Where it is
111 km across · coastline from Natural Earth 10m
Diving in Alaska — 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 | Poor | Poor | Good | Good | Good | Excellent | Excellent | Excellent | Moderate | Poor | Poor | Poor |
| Water temp (°C) | 6 | 6 | 6 | 7 | 9 | 11 | 13 | 14 | 13 | 10 | 8 | 7 |
| Visibility (m) | — | 0–10 | 5–15 | 5–15 | 0–10 | 0–10 | 0–10 | 0–10 | 0–10 | 0–10 | — | — |
| Marine life | Steady | Steady | Peak | Peak | Steady | Steady | Busy | Steady | Steady | Steady | Steady | Steady |
| Best time | Peak | Peak | Peak | Peak |
Excellent Good Moderate PoorPeak season May–Aug
Long-term averages, 2016–2025. Visibility is estimated from satellite chlorophyll-a. Water temperature is the surface mean; it is cooler at depth.
The Alaska diving season
March to August · Peak season
6 monthsJFMAMJJASOND
- Water temperature
- 6–14 °C
- Visibility
- under 10 m
- Rain
- 19 days a month
Diving conditionsRain is frequent topside. The wind eases. The sea is calmer.
Marine lifeCalifornia sea lion (likely) peaks at Alaska in these months.
September · Shoulder season
1 monthJFMAMJJASOND
- Water temperature
- 13–13 °C
- Visibility
- under 10 m
- Rain
- 20 days a month
Diving conditionsSwell is common, and crossings can be rough. This is the wet season topside.
October to February · Off season
5 monthsJFMAMJJASOND
- Water temperature
- 6–10 °C
- Rain
- 21 days a month
Diving conditionsThis is the wet season topside. The wind is up. The sea is rougher.
- Spring tides run 4.0 m against 2.2 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.
Alaska water temperature and weather
6,234 underwater observation records · 30 surveyed years of ocean data · 10 years of sea temperature
Water & weather
Alaska 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
13
rough days a month
Seas top 1.5 m on 43% of days. Enough to cancel a day boat
1
blowy days a month
Gusts over 40 km/h, about where a day boat stays in port
20
wet days a month
9 of them bring heavy rain
| Month | Swell | Gusts over 40 km/h | Wet days | Heavy rain | Air | Daylight |
|---|---|---|---|---|---|---|
| January | 2.9 m | 6% | 22 | 12 | 3 °C | 7.1 h |
| February | 2.6 m | 2% | 18 | 10 | 3 °C | 9.1 h |
| March | 2.5 m | 2% | 18 | 8 | 5 °C | 11.4 h |
| April | 2.1 m | 1% | 18 | 8 | 8 °C | 14.0 h |
| May | 1.8 m | 0% | 19 | 5 | 12 °C | 16.2 h |
| June | 1.5 m | 0% | 19 | 3 | 15 °C | 17.6 h |
| July | 1.2 m | 0% | 17 | 5 | 17 °C | 17.0 h |
| August | 1.5 m | 0% | 20 | 7 | 17 °C | 15.0 h |
| September | 2.3 m | 2% | 20 | 11 | 15 °C | 12.5 h |
| October | 2.8 m | 7% | 22 | 13 | 10 °C | 10.0 h |
| November | 3.0 m | 7% | 22 | 13 | 6 °C | 7.7 h |
| December | 2.7 m | 5% | 22 | 13 | 3 °C | 6.4 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: Poor | February week 1: Poor | March week 1: Moderate | April week 1: Moderate | May week 1: Good | June week 1: Good | July week 1: Excellent | August week 1: Excellent | September week 1: Good | October week 1: Moderate | November week 1: Poor | December week 1: Poor |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Week 2 | January week 2: Poor | February week 2: Poor | March week 2: Moderate | April week 2: Moderate | May week 2: Good | June week 2: Excellent | July week 2: Excellent | August week 2: Good | September week 2: Good | October week 2: Poor | November week 2: Poor | December week 2: Poor |
| Week 3 | January week 3: Poor | February week 3: Moderate | March week 3: Good | April week 3: Good | May week 3: Excellent | June week 3: Excellent | July week 3: Excellent | August week 3: Excellent | September week 3: Poor | October week 3: Poor | November week 3: Poor | December week 3: Poor |
| Week 4 | January week 4: Poor | February week 4: Moderate | March week 4: Good | April week 4: Good | May week 4: Excellent | June week 4: Excellent | July week 4: Excellent | August week 4: Excellent | September week 4: Poor | October week 4: Poor | November week 4: Poor | December week 4: Poor |
Excellent Good Moderate PoorBest week to go: fourth of June
January, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 7 °C | 2.8 m | 22 km/h | 64% |
| Week 2 | Poor | 6 °C | 2.9 m | 23 km/h | 68% |
| Week 3 | Poor | 6 °C | 2.8 m | 22 km/h | 78% |
| Week 4 | Poor | 6 °C | 2.6 m | 22 km/h | 75% |
February, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 6 °C | 2.7 m | 21 km/h | 64% |
| Week 2 | Poor | 6 °C | 2.8 m | 19 km/h | 61% |
| Week 3 | Moderate | 6 °C | 2.4 m | 19 km/h | 63% |
| Week 4 | Moderate | 6 °C | 2.4 m | 20 km/h | 63% |
March, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 5 °C | 2.6 m | 20 km/h | 59% |
| Week 2 | Moderate | 5 °C | 2.4 m | 19 km/h | 59% |
| Week 3 | Good | 5 °C | 2.4 m | 18 km/h | 64% |
| Week 4 | Good | 6 °C | 2.4 m | 16 km/h | 59% |
April, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 6 °C | 2.4 m | 18 km/h | 64% |
| Week 2 | Moderate | 6 °C | 2.3 m | 18 km/h | 64% |
| Week 3 | Good | 7 °C | 1.9 m | 15 km/h | 57% |
| Week 4 | Good | 7 °C | 1.9 m | 16 km/h | 59% |
May, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 8 °C | 2.0 m | 17 km/h | 60% |
| Week 2 | Good | 8 °C | 1.9 m | 16 km/h | 58% |
| Week 3 | Excellent | 9 °C | 1.5 m | 16 km/h | 56% |
| Week 4 | Excellent | 9 °C | 1.6 m | 16 km/h | 69% |
June, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 10 °C | 1.8 m | 16 km/h | 76% |
| Week 2 | Excellent | 11 °C | 1.8 m | 15 km/h | 67% |
| Week 3 | Excellent | 11 °C | 1.3 m | 14 km/h | 59% |
| Week 4 | Excellent | 12 °C | 1.1 m | 14 km/h | 56% |
July, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 12 °C | 1.1 m | 13 km/h | 47% |
| Week 2 | Excellent | 13 °C | 1.3 m | 13 km/h | 51% |
| Week 3 | Excellent | 13 °C | 1.5 m | 14 km/h | 65% |
| Week 4 | Excellent | 13 °C | 1.2 m | 14 km/h | 61% |
August, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 14 °C | 1.3 m | 14 km/h | 55% |
| Week 2 | Good | 14 °C | 1.7 m | 16 km/h | 63% |
| Week 3 | Excellent | 14 °C | 1.6 m | 16 km/h | 68% |
| Week 4 | Excellent | 14 °C | 1.5 m | 15 km/h | 65% |
September, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 13 °C | 1.7 m | 15 km/h | 63% |
| Week 2 | Good | 13 °C | 1.9 m | 16 km/h | 59% |
| Week 3 | Poor | 12 °C | 2.5 m | 18 km/h | 69% |
| Week 4 | Poor | 12 °C | 2.6 m | 19 km/h | 76% |
October, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 11 °C | 2.4 m | 19 km/h | 69% |
| Week 2 | Poor | 11 °C | 2.4 m | 20 km/h | 73% |
| Week 3 | Poor | 10 °C | 2.6 m | 21 km/h | 77% |
| Week 4 | Poor | 10 °C | 3.3 m | 20 km/h | 68% |
November, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 9 °C | 3.2 m | 22 km/h | 71% |
| Week 2 | Poor | 9 °C | 2.8 m | 22 km/h | 77% |
| Week 3 | Poor | 8 °C | 3.0 m | 21 km/h | 76% |
| Week 4 | Poor | 8 °C | 2.8 m | 21 km/h | 72% |
December, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 8 °C | 2.5 m | 23 km/h | 71% |
| Week 2 | Poor | 7 °C | 2.7 m | 23 km/h | 70% |
| Week 3 | Poor | 7 °C | 2.7 m | 22 km/h | 67% |
| Week 4 | Poor | 7 °C | 2.7 m | 22 km/h | 68% |
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: dry | February: dry | March: dry | April: dry | May: dry | June: dry | July: dry | August: 7 mm | September: dry | October: dry | November: dry | December: dry |
- Sep–Juldrysuit
- Aug7 mm semi-dry
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
No tropical storm has come within 250 km in 30 years of records. Swell and wind set the season, not cyclones.
- 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
Alaska marine life — what you'll see diving
| Species | When | Observed window | Reliability | Evidence | Records |
|---|---|---|---|---|---|
| Harbour seal | All year | Near-guaranteed | 165 | ||
| Grey whale | Apr | Near-guaranteed | 700 | ||
| Orca | Jun–Jul, Sep | Near-guaranteed | 212 | ||
| Sperm whale | Jun–Jul | Likely | 35 | ||
| California sea lion | Mar–Apr | Likely | 23 | ||
| Minke whale | Jun–Jul | Likely | 18 | ||
| Humpback whale | Mar, Jul–Sep | Near-guaranteed | 5076 |
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 Alaska — common questions
- When is the best time to dive Alaska?
- You come for Sitka's cold-water walls, kelp and Steller sea lions. That does not change through the year, so go when the weather is best: May to August.
- When is the diving season in Alaska?
- The diving season in Alaska runs May to August.
- Is the diving in Alaska good for beginners?
- Not really. It is for experienced divers, so it is not a place to learn or to make your first dives after certification.
- How warm is the water in Alaska?
- Between 6 and 14 °C at the surface across the year, coldest in March and warmest in August. It runs cooler below the thermocline.
- What wetsuit do I need in Alaska?
- A drysuit covers the coldest water of the year. In the warmest months a 7 mm semi-dry is enough.
- What is the visibility like in Alaska?
- Roughly 0 to 15 m depending on the month. That is estimated from satellite chlorophyll-a rather than measured in the water.
- What will I see diving Alaska?
- The most consistently recorded species are Harbour seal (near-guaranteed), Grey whale (near-guaranteed) and Orca (near-guaranteed), from 6,234 records within 60 km.
- Does Alaska get tropical storms?
- No. None has passed within 250 km in 30 years of records.
- Is there current in Alaska?
- The tide rises and falls 4.0 m around the full and new moon, against 2.2 m in between. How much of that becomes current depends on the shape of the channel.
- When should I avoid Alaska?
- October–January are the weakest months for conditions.
- How do you dive Alaska?
- Mostly from day boats. Trips run through the season, May–Aug.