Question 1

What does the MISO footprint cover?

Accepted Answer

The Midcontinent Independent System Operator coordinates the bulk power system across 15 U.S. states and the Canadian province of Manitoba, stretching from the Iron Range of Minnesota all the way to the Louisiana Gulf coast. The footprint is non-contiguous — the south region (Mississippi, Louisiana, parts of Arkansas and east Texas) is physically separated from the north and central regions by an intervening Tennessee Valley Authority footprint. Energy transfers between MISO South and MISO North/Central are limited to roughly 3 GW, a constraint that has tightened during winter cold weather and summer heat.

Question 2

What does the MISO generation mix look like?

Accepted Answer

MISO has one of the most diverse generation mixes in North America. Wind dominates Iowa, Minnesota, North Dakota, and South Dakota, with Iowa generating more than half its electricity from wind in recent years. Coal still anchors much of Indiana, Missouri, and Wisconsin, although retirements are accelerating. Nuclear units in Illinois (the largest nuclear fleet in any U.S. state), Michigan, Wisconsin, Minnesota, and Louisiana provide steady baseload. Natural gas combined-cycle plants are concentrated along the Mississippi River corridor and in the south region. Solar is growing rapidly across the central footprint.

Question 3

What weather events most stress the MISO grid?

Accepted Answer

The MISO footprint contains three distinct climate regimes that each generate their own emergencies. The northern tier (Minnesota, Wisconsin, the Dakotas, Upper Michigan) experiences brutal Canadian-origin Arctic outbreaks with wind chills below -50°F. The central corridor (Iowa, Illinois, Indiana, Lower Michigan, Missouri) sees hot humid summers and severe convective weather — including the historic August 2020 derecho that crossed Iowa with 140 mph straight-line winds. The south region (Arkansas, Mississippi, Louisiana) is shaped by Atlantic and Gulf hurricanes that periodically batter the Louisiana coast (Ida, Laura, Delta, Zeta) and drive multi-day load reductions across the petrochemical corridor.

Question 4

What weather alerts dominate the northern MISO footprint in winter?

Accepted Answer

Minnesota, Wisconsin, the Dakotas, and Upper Michigan see frequent Winter Storm Warnings, Blizzard Warnings, and Wind Chill Warnings throughout the December–March stretch. Wind Chill Warnings are typically issued when wind chills are forecast to fall below -35°F, criteria routinely met during Canadian-origin Arctic outbreaks. Lake-effect snow off Lake Superior produces additional Lake Effect Snow Warnings across the Upper Peninsula and northern Wisconsin, and ice storms moving through Minnesota and northern Iowa drive Ice Storm Warnings several times each winter.

Question 5

How does the National Weather Service warn for derechos in the central Midwest?

Accepted Answer

Derechos — long-lived bands of damaging straight-line wind from organized thunderstorm complexes — are warned for in real time through Severe Thunderstorm Warnings (often with the 'destructive' tag for winds above 80 mph) and Tornado Warnings if embedded circulations develop. The Storm Prediction Center's day-1 and day-2 convective outlooks routinely flag the central MISO footprint for damaging-wind potential. The August 2020 Iowa derecho remains the benchmark event, having caused widespread transmission and distribution damage across Iowa and Illinois.

Question 6

What weather drives MISO South's biggest emergency events?

Accepted Answer

MISO South — Mississippi, Louisiana, Arkansas, and east Texas — is shaped by Atlantic and Gulf hurricanes from June through November and by the same Arctic outbreaks that periodically reach all the way to the Gulf coast in winter. Hurricane Watches and Warnings from the National Hurricane Center, Storm Surge Warnings for the Louisiana coast, and Winter Storm Warnings during cold-air intrusions are the main alert types. Major hurricane landfalls (Ida, Laura, Delta, Zeta) have driven multi-week distribution outages across south Louisiana.

Question 7

How are heat waves forecast across MISO in summer?

Accepted Answer

The National Weather Service issues Heat Advisories when forecast heat indices reach 100°F to 105°F and Excessive Heat Warnings when they exceed 105°F to 110°F for two or more hours, with thresholds varying by region based on climatology. Across MISO's central corridor — Iowa, Illinois, Indiana, Lower Michigan, Missouri — these alerts are most common in late July and August. Multi-day heat events that overlap several states drive the highest summer cooling loads.

Question 8

What role does the Climate Prediction Center play for MISO winters?

Accepted Answer

The CPC's 6–10 day and 8–14 day outlooks give probabilistic guidance on whether the upcoming period will tilt above or below normal in temperature. Across the MISO footprint these outlooks are watched closely for early signals of polar vortex disruptions and Arctic outbreak risk. Below-normal temperature shading across the northern tier 8 to 14 days out is one of the earliest leading indicators of significant winter cold and the heating-driven peaks that follow.

Question 9

What sources are referenced for the historical events on this page?

Accepted Answer

Specific event references on this page (the August 2020 Iowa derecho, Hurricanes Ida, Laura, Delta, and Zeta) are drawn from the NWS Weather Prediction Center storm-event summaries, the NWS Des Moines and Quad Cities damage surveys, the National Hurricane Center's Tropical Cyclone Reports at nhc.noaa.gov, and MISO's published market notices and reliability reports at misoenergy.org.

Metric	Actual	Normal	Departure
CDD	229.6	91.5	+138.1
HDD	2941.2	3162.5	-221.3

MISO

Temperature Forecast

Precipitation Chance

Recent History (7 days)

MISO (Midcontinent ISO) — Frequently Asked Questions

All Sources for MISO