New York · Multiple shoreline counties County
Lake Ontario
Rochester · Oswego · Sodus Point · Sackets Harbor
Loading live conditions for Lake Ontario…
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"The smallest Great Lake by surface area but one of the deepest — which means a slow, late-arriving swim season. Spring water stays cold long after the air warms, then nearshore temps peak in the low 70s in August along the sandy eastern shore, from Sodus Point to the dunes near Sackets Harbor."
Seasonal pattern
When does Lake Ontario warm up?
Lake Ontario is deep (max depth 802ft) and carries significant thermal inertia, so it warms slowly — surface temperatures typically don't reach comfortable swimming range until late June or early July. Spring-fed or alpine lakes stay cooler all summer. The live forecast above shows current conditions.
Field notes
About Lake Ontario
- Deep for its size (802 ft) — warms late and cools late
- Eastern-shore beaches (Sodus Point, Sandy Island) get the warmest water
- August is the swim month — spring temps lag the air by weeks
- Lake-effect machine: this water powers Tug Hill's legendary snow each winter
- Surface area
- 4,850,000 acres
- Max depth
- 802 ft
- County
- Multiple shoreline counties
- Water data
- Modeled estimate from air-temp trends