MISO absorbed two extreme weather shocks in three weeks. On August 11, a derecho, a high-intensity windstorm, crossed the footprint from Iowa to the Ohio Valley with 99 mph gusts, cutting power to more than 1 million customers. From August 31 to September 4, a heat dome pushed demand to 123 GW, a new September record.

The two events pushed spreads in opposite directions. The derecho cut the real-time four-hour top-bottom (TB4) spread at Indiana Hub from $555/MW-day on August 10 to $196/MW-day on the storm day. Spreads kept falling into August 12, bottoming at $54/MW-day, a 90% collapse. The heat dome, in contrast, lifted spreads to $5,971/MW-day. That was 17 times the average MISO North battery's daily revenue in August.

Extreme weather is increasingly common in MISO, but it only pays battery energy storage systems (BESS) when it tightens the system. Storms that cause widespread outages knock out demand, which suppresses prices even as the same storms force wind generation to curtail. The heat dome instead left record demand outrunning available supply. A battery selling through the 25 pinned minutes at the $10,000/MWh cap could have earned 12 days of an average August's revenue.

Key takeaways

• Extreme weather is increasing in MISO. Tornado reports in the North and Central regions ran 141% above the five-summer average this summer, and heat-dome days climbed 21% against the same baseline.
• Extreme weather can knock out demand and suppress prices even while forcing wind generation offline. The derecho cut wind just 0.9 GW on the storm day, while load ran up to 4.5 GW below forecast the next day.
• The September 2 heat dome pinned 5-minute real-time prices at Indiana Hub at MISO's $10,000/MWh Value of Lost Load cap for 25 minutes. MISO approximately tripled that cap from $3,500/MWh last September, raising the reward for capturing real-time spikes.
• A fully real-time 100 MW battery could have earned $631k on September 2, 14 times its derecho-day total.

Extreme weather is increasing in MISO: Indiana tornado reports rose 692% this summer

A derecho is a windstorm producing straight-line wind damage along a path at least 400 miles long and 60 miles wide, with gusts of 58 mph or higher. On August 11, gusts reached 99 mph at Gary, Indiana, and the storm produced at least eight confirmed tornadoes. Parts of northwest Indiana went two weeks without power.

Extreme wind is shifting into the footprint. Tornado reports ran 275% to 692% above the five-summer average in Illinois, Missouri, and Indiana, continuing the shift east out of Southwest Power Pool (SPP) territory and into MISO.

Extreme heat is climbing the same way. June to August 2026 was the warmest US summer on record as El Niño strengthened. Indianapolis recorded 17 heat-dome days this summer against a five-summer average of 13. A heat-dome day is any day in a run of three or more consecutive days at or above 90°F.

The pattern has precedent. Modo Energy's July benchmark traced two heatwaves in one month. A county-level study of US outages found an outage of eight hours or longer is 52 times more likely when extreme heat compounds with storm winds and heavy rain.

The same study splits MISO's outage risk: the North is most sensitive to high winds with moderate heat, the South to prolonged heatwaves. Both of this summer's events landed hardest in the North and Central regions. It also flags North American Electric Reliability Corporation (NERC) projections of capacity deficits there.

For developers, that moves extreme-weather exposure from an SPP siting problem to a MISO one.

The derecho collapsed spreads by 90% instead of spiking them

Storm damage on this scale suggests a supply shock, as storms force wind turbines offline and damage physical assets. The data shows widespread outages on the demand side instead: losing more than 1 million customers cut load, not generation. However, wind generation ran up to 41% below the prior day's same hour during the storm.

MISO systemwide load averaged 2.5 GW below forecast on August 12, with hourly gaps reaching 4.5 GW, 4% of forecast demand. Peak demand fell 4% from 117 GW on August 10 to 112 GW on August 12. Demand restoration ran for days, so the price trough came the day after the storm.

Real-time prices settled below day-ahead on August 12 and 13. The real-time TB4 spread at Indiana Hub fell to $54/MW-day on August 12 while the day-ahead spread held at $397/MW-day. Day-ahead-committed batteries locked in seven times the spread available to real-time merchant dispatch.

Prices pinned at the $10,000/MWh cap for 25 minutes on September 2

The heat dome had the opposite impact of the wind event. On September 1, Indiana Hub hourly real-time prices reached $1,154/MWh in the evening peak. September 2 went further: demand set the September record.

Thinning supply pinned prices against record demand. Solar generation fell from its 18 GW midday peak to zero into the evening, and net imports dipped to 7.9 GW in the pinned hour. Five-minute real-time prices at Indiana Hub jumped from $843/MWh at 6:45 PM to MISO's $10,000/MWh Value of Lost Load cap at 7 PM. They held there for 25 minutes.

A footprint-wide Maximum Generation Event began at 6:44 PM and escalated to Step 2 at 7:11 PM, in the middle of the pin. MISO reported that higher-than-forecast load and a loss of import interchange schedules were among its emergency causes.

What could a battery have captured?

For a battery, the pin translated directly into spread. The real-time TB4 spread reached $5,971/MW-day at Indiana Hub, second only to Michigan Hub's $6,163/MW-day. That is 17 times what an average MISO North battery earned per day in August.

MISO's battery fleet took advantage of the system stress. Discharge peaked at 608 MW in the hour before the pin and held 534 MW through it. A battery discharging through the pin could have earned $4,167/MW in those 25 minutes alone, against the $5,971/MW-day full-day spread.

Ancillary service prices spiked alongside energy, since co-optimization makes them carry the opportunity cost of energy. MISO-wide real-time regulation cleared at $1,253/MWh in the pinned hour, giving batteries two avenues to heightened revenue.

What this means for MISO BESS developers

Developers should focus on the extreme weather that moves prices footprint-wide. The derecho created no top-bottom spread value at the hub, only localized disruption. The heat dome moved prices in every zone, and that is the exposure worth building for.

Hedging matters given MISO's volatility and elevated heat. A day-ahead hedge caps the downside in storm events but surrendered 85% of the September 2 upside, when day-ahead cleared at $878/MW-day against the $5,971/MW-day real-time spread.

The higher Value of Lost Load raises the tail of real-time prices. With the cap at $10,000/MWh, holding capacity for the real-time market matters more, because the pinned minutes now pay approximately three times what they could a year ago.