North Country · Lake Ontario Plain
Jefferson County weather and solar
What the climate here actually does to a solar array — production by season, the structural spec the snow load forces, and the roof decisions that follow from both.
The climate
Lake Ontario Plain
Specific yield
1,080–1,220 kWh / kW-DC / yr
A 10 kW array averages about 11,500 kWh a year here.
Modeled NREL PVWatts v8 · verified Jan 2026
Mean annual snowfall
80–140 inches
Heavy lake-effect exposure from Lake Ontario.
Modeled NOAA/NWS seasonal snowfall records · verified Jan 2026
Design ground snow load
50–80 psf
Racking and structural review are engineered to this figure. Ask which number your proposal used.
Filed ASCE 7 ground snow load data · verified Jan 2026
Winter quarter share
10% of annual
December, January, and February combined.
Derived NREL PVWatts v8 · verified Jan 2026
Days with snow on the array
25–55 per season
Far fewer than days with snow on the ground — panels shed.
Observed GridReady quote and bill review sample · verified Jan 2026
Seasonality
Production month by month on a 10 kW array
kWh per month from a 10 kW-DC array at the midpoint of the Lake Ontario Plain yield band. Bar height is relative to the peak month.
Show the arithmetic
10 kW × 1,150 kWh/kW/yr (midpoint of the Lake Ontario Plain band) = 11,500 kWh a year, distributed on a northern-temperate seasonal curve anchored so December through February sums to 10% of the total.
A modeled shape, not a measurement of your roof. Orientation, pitch, and shading move individual months more than they move the annual total.
Derived NREL PVWatts v8 · verified Jan 2026
Local weather
What the weather here specifically does
- Because Ontario does not freeze, this belt keeps producing snow into March in a way the Erie belt does not.
- The first few miles inland from the shore see sharply more snow than the shore itself. Elevation gain of even a couple hundred feet shows up in the totals.
- Fruit-belt agriculture along the shore means open land and generally unshaded roofs.
The roof
Consequences for the array itself
- Wind exposure along the immediate shore is significant.
- Snow load rises quickly with distance inland. Two addresses in the same town can carry different design loads.
The one question worth asking every installer here
“What ground snow load is this racking engineered for, and can I see the stamped calculation?” The right answer in Jefferson County is 50–80 psf. At this load, structural review is genuine engineering and some roofs will need reinforcement. That is a finding, not a sales objection.
Microclimates
Jefferson County is not one climate
| Zone | Snowfall | Snow load | Specific yield |
|---|---|---|---|
| Lake Ontario Plain (primary) | 80–140" | 50–80 psf | 1,080–1,220 kWh/kW |
| Tug Hill Plateau | 150–250" | 90–150 psf | 980–1,120 kWh/kW |
By location
Elevation across Jefferson County
| Place | Elevation | Climate zone | Guide |
|---|---|---|---|
| Watertown | 500 ft | Lake Ontario Plain | Costs & production |
Questions
Jefferson County climate FAQ
- How much does snow reduce solar production in Jefferson County?
- Less than most people expect. A pitched array here sees roughly 25 to 55 days a season with enough cover to stop production — the glass is slick and the array runs warmer than the shingles around it. Cloud cover through November and December costs more production than snow cover does. What snow really drives is the structural spec: design ground snow load here is 50 to 80 psf, and racking must be engineered and stamped for it.
- What is the seasonal production curve in Jefferson County?
- Jul is the strongest month and Dec the weakest, by roughly 4.4 to one. December through February combined account for about 10% of annual output — roughly one month's worth of production spread across three months. A proposal that shows a smooth, near-flat monthly production curve for this county is not modeling this climate.
- Is Jefferson County too far north or too cloudy for solar?
- No, but the honest framing is that the climate sets the ceiling and the electricity rate sets the value. A 10 kW array here produces roughly 11,500 kWh a year. That is real output — the question is what a kWh is worth where you live, which is a rate question rather than a weather one.
- How does lake-effect snow affect solar in Jefferson County?
- Heavy exposure from Lake Ontario. Because Ontario does not freeze, this belt keeps producing snow into March in a way the Erie belt does not.
- Does cold weather help or hurt solar panels in Jefferson County?
- Cold helps efficiency — panels produce more per unit of sunlight at low temperature, which is why a clear February day can outperform a hazy July one on a per-hour basis. What hurts is daylight hours and cloud cover, and this climate is short on both between November and February. The two effects do not cancel out; the daylight loss dominates.
Next step
Turn this into your own numbers
The climate sets what a roof can produce. Your rate sets what that production is worth, and your roof sets how much of the band you actually get.
How this page is built
This is a generated page: the structure is shared across locations, the numbers are not. Every figure comes from the source cited beside it, with the date we last checked it. Nothing here is a quote, an appraisal, or tax advice, and none of it is specific to your roof.
Rates and incentive programs change. We re-verify utility tariffs and NYSERDA program status on a rolling schedule and stamp the date on each number rather than on the page, so you can see which specific figures are fresh. Full methodology · Program status tracker · About the Local Energy Playbook
Page content last reviewed April 2026.