On Lake Ontario, our weather in summer is mostly placid, with occasional storms, but no hurricanes. The gradient flow is from the south and west. Rochester harbor is actually located at the center of a cove about 3 miles deep (see the chart graphic, at right). In a typical summer thermal, the breeze that starts out in the southwest tends to bend to the west around Braddocks Point as the land warms, though not always. I once advised visiting sailors that the morning breeze would be 230° and would go as far right as 310° as the day went on. Paraphrasing Stuart Walker’s assessment of Rochester conditions, I said go left on the first beat, and right thereafter. And I was correct, but only on the fifth and final day of the regatta.
Most of us have learned that you "hit the beach" on a Wednesday night race, since the cooling land brings the wind left again, but we also know how often this proves wrong for whatever reason (usually velocity). During the boating season, winds of over 16 knots occur less than 20% of the time – less than 15% in June and July.
In reality there is no "typical" wind off Rochester. What we do get tends to be steady, if hard to predict, which is one of the things that makes Lake Ontario such an interesting regatta site. Current is rarely a factor on Lake Ontario, although there are variable, sometimes strong, eddies on either side of the main current exiting the Genesee River.
Autumn weather is another matter, though, with persistent southwesterly gales and high seas. The gradient, reinforced by the proximity of the Jet Stream during the Equinox and a fluctuating barometer, brings strong, dense air which kicks up big seas in a short time.
Water temperature is perhaps the biggest contributor to the lake’s conditions and to our enjoyment of them. A comparison of average monthly air and water temperatures on Lake Ontario during the boating season indicates that the water warms in quite direct proportion to the daily average temperature, up to its peak of 68° in August.
For more information, please see the book Sailor’s Wind by Stuart Walker which contains a section on Rochester.