Blue Lagoon Water Temperature & Swim Forecast

The sea in Blue Lagoon peaks in August, when the water averages around 27°C.

The main swimming season runs from June – November, when surface temperatures stay comfortable for extended sessions.

On average, 6 months a year sit above 20°C — the threshold most swimmers describe as pleasant without a wetsuit.

Shoulder months like May and December are noticeably cooler but often quieter, with fewer crowds and steadier weather.

Outside peak season the water drops toward 17°C, so a 3/2mm shorty or full wetsuit makes long swims much more comfortable.

The coldest month is typically February at around 15°C, when cold-water swimmers dominate the coast.

Long-term climatology for Blue Lagoon shows an annual mean sea temperature of 20°C, ranging from 15°C in winter to 27°C at the summer peak.

The seasonal swing is roughly 12°C between the coldest and warmest month — a useful yardstick when comparing years or checking whether the current sea is running above or below average.

Recent decades have trended slightly warmer at Blue Lagoon, in line with regional sea-surface temperature records for the wider basin.

Monthly averages below are drawn from multi-decadal climatology and are updated as new observations arrive.