Sunnyside Beach Water Temperature & Swim Forecast
Ontario family beach.
Mild water with a light chop and a light breeze — comfortable conditions for most swimmers.
Model estimate · modelled, not a buoy measurement. How accurate is this?
Location
Sunnyside Beach on the map, with nearby beaches and live sea temperatures.
7-day forecast
Water, air, waves, wind and UV outlook for the week ahead.
3/2mm fullsuit
At 18.9°C a 3/2mm fullsuit is the standard wetsuit for surfing and watersports.
Recommendation tuned for Sunnyside Beach's current water temperature. Individual tolerance, wind chill, and session length all matter — when in doubt, size up.
Sunnyside Beach swimming conditions summary
- Water temperature
- 18.9°C
- Water feels
- Refreshing
- Swimmable today
- Yes, but fresh — short swims or a wetsuit
- Swim conditions score
- 70/100 · Good
- Wetsuit needed
- 3/2mm fullsuit
- Air temperature
- —
- Waves
- —
- Wind
- —
- UV index
- —
- Average sea temperature (September)
- 19.0 °C
- Warmest months to swim
- July, August, September
At 18.9°C a 3/2mm fullsuit is the standard wetsuit for surfing and watersports. Model estimate. Water, wave, wind and UV values are Open-Meteo marine/weather model estimates, refreshed hourly — not buoy measurements.
Frequently asked questions
Can I swim at Sunnyside Beach right now?
The sea at Sunnyside Beach is currently 18.9°C — fresh swimming conditions. Most swimmers will find the water comfortable when it's above 22°C; below 18°C feels fresh and a wetsuit is recommended.
What will the sea temperature be at Sunnyside Beach next week?
Based on long-term September averages and the latest marine model, expect the sea around Sunnyside Beach to sit close to 14.7°C over the next 7 days. Check the live 7-day chart above for the exact daily outlook.
When is the best month to swim at Sunnyside Beach?
July – August – September are typically the warmest months to swim at Sunnyside Beach, with sea temperatures at their seasonal peak.
Do I need a wetsuit at Sunnyside Beach?
With water currently at 18.9°C: above 22°C no wetsuit needed; 18–22°C a shorty is comfortable for long swims; 14–18°C a 3/2mm full suit; below 14°C a 4/3mm or thicker.
Can I swim at Sunnyside Beach today?
The sea is currently 18.9°C — good swimming conditions. Most swimmers will find it pleasant.
- • Located in Ontario, Canada (Lake Ontario).
- • Family friendly with calm, accessible water.
- • Live data refreshed hourly from Open-Meteo Marine.
Monthly sea temperature averages
Tap any month to see what to expect — based on regional climatology.
Best time to swim in Sunnyside Beach
The sea in Sunnyside Beach peaks in August, when the water averages around 22°C.
The main swimming season runs from July – August, when surface temperatures stay comfortable for extended sessions.
On average, 2 months a year sit above 20°C — the threshold most swimmers describe as pleasant without a wetsuit.
Shoulder months like June and September are noticeably cooler but often quieter, with fewer crowds and steadier weather.
Outside peak season the water drops toward 7°C, so a 3/2mm shorty or full wetsuit makes long swims much more comfortable.
The coldest month is typically February at around 0°C, when cold-water swimmers dominate the coast.
Sunnyside Beach sea temperature history
Long-term climatology for Sunnyside Beach shows an annual mean sea temperature of 10°C, ranging from 0°C in winter to 22°C at the summer peak.
The seasonal swing is roughly 22°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 Sunnyside Beach, 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.
Sunnyside Beach sea temperature: frequently asked questions
What is the warmest month to swim in Sunnyside Beach?
August is the warmest month in Sunnyside Beach, when the sea averages about 22°C. Late-season warmth often persists a few weeks after peak.
When is the sea coldest in Sunnyside Beach?
The coldest month in Sunnyside Beach is typically February, when the water averages around 0°C. Cold-water swimmers and surfers dominate this period.
When can you swim in Sunnyside Beach without a wetsuit?
The main swimming season in Sunnyside Beach runs from July – August — about 2 months a year when the sea sits above 20°C, the level most swimmers describe as pleasant without a wetsuit.
Do I need a wetsuit in Sunnyside Beach?
Outside peak summer the water in Sunnyside Beach drops toward 7°C, so a 3/2mm shorty or full wetsuit makes long swims much more comfortable. In peak months most swimmers go without.
What is the average sea temperature in Sunnyside Beach?
The long-term annual mean sea temperature in Sunnyside Beach is about 10°C, based on multi-decadal climatology of the surrounding waters.
How do I check the current sea temperature in Sunnyside Beach?
The live reading at the top of this page shows the current sea temperature in Sunnyside Beach, updated hourly from marine buoy and satellite data. The 7-day forecast covers water, air, waves, wind and UV for the week ahead.
Year-round sea temperature
Best swim months: Jul – Aug
| Month | Sea | Comfort |
|---|---|---|
| Jan | 1°C | Cold |
| Feb | 0°C | Cold |
| Mar | 1°C | Cold |
| Apr | 4°C | Cold |
| May | 10°C | Cold |
| Jun | 16°C | Bracing |
| Jul | 21°C | Pleasant |
| Aug ⭐ | 22°C | Warm |
| Sep | 19°C | Pleasant |
| Oct | 13°C | Cold |
| Nov | 7°C | Cold |
| Dec | 3°C | Cold |
Nearby beaches
The closest coastline, with live water temperatures.