Live market data
ISO-NE temperature forecast
ISO New England's own weather forecast, zone by zone — the input behind every demand number on this site.
Fetching the latest published forecast…
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ISO New England's own weather forecast, zone by zone — the input behind every demand number on this site.
How cold will it get across New England?
ISO-NE forecast temperature peaks at 78 °F on Fri, 3 PM, against a low of 59 °F — a swing of 19 °F across the window. Southeast Mass. is the heaviest area at 84 °F.
Plotted window Aug 28, 3:00 AM EDT → Aug 29, 3:00 AM EDT. Reissued with each load-forecast vintage; the latest is shown.
Every line above, and who produced it.
The grid operator's own published forecast for these hours. Source: ISO New England.
The same window, split by zone — each area’s own curve.
Every hour of the window, shaded by load.
| 0 | 6 | 12 | 18 | |||||||||||||||||||||
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| Fri, 8/28 |
| Zone | Peak (°F) | Peak hour | Low (°F) | Average (°F) |
|---|---|---|---|---|
| Southeast Mass. | 84 | Fri, 2 PM | 65 | 74 |
| New Hampshire | 84 | Fri, 4 PM | 51 | 71 |
| Northeast Mass./Boston | 83 | Fri, 3 PM | 65 | 74 |
| Rhode Island | 82 | Fri, 3 PM | 65 | 72 |
| West/Central Mass. | 80 | Fri, 3 PM | 55 | 70 |
| Forecast | Produced by | Method | Horizon |
|---|---|---|---|
| Average across zones | ISO New England | ISO-NE weather forecast by load zone | As far as the operator publishes, hourly |
A point forecast with no confidence interval, and the error compounds downstream: a two-degree miss across a whole footprint moves the demand forecast by more than most people expect, which is why the load forecast is read alongside this rather than on its own.
The temperature ISO New England is forecasting for each of the eight ISO-NE load zones, plus the average across them. This is the operator's own weather call, published with its load forecast rather than taken from a separate weather service — so it is the same input the demand forecast was built from.
New England's grid is tested by cold, not heat. Temperature is the input its load forecast is built on, and in winter it is also a fuel-supply forecast: the same gas that heats homes runs the power plants, so a cold morning tightens both sides of the balance at once.
In winter, watch the overnight lows rather than the daily highs. That is when heating demand and gas constraints meet, and it is the hour ISO-NE plans hardest around.
curl "https://askthegrid.com/api/v1/grid/radar/curves?iso=ISONE&horizon=extended"
Connect your agent to mcp.askthegrid.com and this forecast is a tool call away — the same host Claude and ChatGPT connectors already use.
It is the weather forecast the grid operator itself publishes and builds its demand forecast on. That makes it more useful than a general forecast for this purpose: it is the exact input behind the load numbers, at the zone boundaries the market actually uses.
Because New England has no in-region gas production and limited pipeline capacity. On the coldest days gas is committed to heating first, so a cold forecast raises demand and reduces the fuel available to serve it in the same move.
A great deal, and non-linearly. Past a comfort band, each additional degree adds more demand than the last, because more air conditioning or heating switches on and runs for longer — which is why forecast error matters most on the days that are already extreme.
| Sat, 8/29 |
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Darkest cells are the tightest hours. The window peaks at 78 °F on Fri, 3 PM, local to the market.
| Connecticut | 80 | Fri, 4 PM | 60 | 72 |
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| Vermont | 76 | Fri, 1 PM | 48 | 65 |
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| Maine | 61 | Fri, 9 PM | 60 | 61 |
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