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open lake forecast for lake ontario
national weather service buffalo ny
402 am edt tue jul 21 2026

for waters beyond five nautical miles of shore on lake ontario

waves are the significant wave height - the average of the highest
1/3 of the wave spectrum. occasional wave height is the average of
the highest 1/10 of the wave spectrum.

.synopsis...
a 29.4 inch low will be near james bay with multiple frontal 
boundaries crossing the lake through tonight. a secondary cold front 
will cross the lake wednesday, with a 30.1 inch high building across 
the lower great lakes region wednesday night through friday. the 
high will move off the east coast saturday.


loz063>065-211500-
lake ontario open waters from hamlin beach to the saint lawrence
river-
402 am edt tue jul 21 2026

.today...south winds 15 to 20 knots. showers with a chance of
thunderstorms late this morning. showers with thunderstorms
likely this afternoon. some thunderstorms may produce gusty winds
from late morning on. waves 2 to 4 feet building to 3 to 5 feet,
then subsiding to 2 to 4 feet. 
.tonight...south winds 10 to 15 knots becoming west 15 to
20 knots. showers likely with a chance of thunderstorms in the
evening, then a chance of showers and thunderstorms after
midnight. a chance of showers late. some thunderstorms may
produce gusty winds in the evening. waves 2 to 4 feet building to
3 to 6 feet. 
.wednesday...west winds 15 to 25 knots. waves 5 to 8 feet. waves
occasionally around 10 feet. 
.wednesday night...west winds 15 to 25 knots diminishing to 10 to
15 knots. waves 5 to 8 feet subsiding to 2 to 4 feet. waves
occasionally around 10 feet. 
.thursday...west winds 5 to 15 knots becoming southwest less than
10 knots. waves 1 to 3 feet subsiding to 1 foot or less. 
.friday...south winds 10 knots or less. waves 1 foot or less. 
.saturday...south winds 10 knots or less. waves 1 foot or less. 

winds and waves higher in and near thunderstorms.

$$

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forecast for the saint lawrence river
including the thousand islands region
national weather service buffalo ny
403 am edt tue jul 21 2026


slz022-024-211500-
saint lawrence river from cape vincent to saint regis
403 am edt tue jul 21 2026

.today...south winds 10 to 15 knots. a chance of showers late
this morning. showers with a chance of thunderstorms this
afternoon. some thunderstorms may produce gusty winds from late
morning on. 
.tonight...south winds 5 to 15 knots becoming southwest. showers
likely with a chance of thunderstorms through the early
overnight, then a chance of showers late. some thunderstorms may
produce gusty winds in the evening. 
.wednesday...southwest winds 5 to 15 knots becoming west. a
chance of showers. 
.wednesday night...west winds 5 to 10 knots. a chance of showers
in the evening. 
.thursday...southwest winds 10 knots or less. mainly clear. 
.friday...southwest winds less than 10 knots. mainly clear, then
becoming partly cloudy. 
.saturday...south winds less than 10 knots. mainly clear, then
becoming partly cloudy. 

winds and waves higher in and near thunderstorms.

$$