Question 1

What does the SPP footprint cover?

Accepted Answer

Southwest Power Pool operates the bulk transmission system across the central United States, with a footprint that historically spanned Kansas, Nebraska, Oklahoma, the Dakotas, and parts of surrounding states. Effective April 1, 2026, SPP expanded westward to incorporate the Colorado Front Range (Denver, Colorado Springs), southeastern Wyoming (Cheyenne), and a portion of north-central Montana (Great Falls), bringing former Western Area Power Administration and other entities into the SPP footprint. The expansion stretches SPP from the Canadian border to the Texas Panhandle and from the Mississippi River nearly to the Rockies.

Question 2

What does the SPP generation mix look like?

Accepted Answer

SPP leads the United States in wind generation as a percentage of total system load, with annual wind energy share periodically exceeding 50%. Oklahoma, Kansas, and the Texas Panhandle host massive wind resources along the I-35 and Caprock corridors. Coal remains a significant share of the generation mix, particularly in Wyoming, Kansas, and Oklahoma, although retirement schedules are accelerating. Natural gas combined-cycle capacity is concentrated in the eastern footprint and in Oklahoma. Nuclear contributions come from Wolf Creek (Kansas) and Cooper (Nebraska). Hydro from the Missouri River dams contributes baseload and flexibility. Solar and battery storage are growing, especially in Oklahoma and the new Colorado footprint.

Question 3

What weather events most stress the SPP grid?

Accepted Answer

SPP sits in the heart of Tornado Alley, and the defining historical event is Winter Storm Uri in February 2021 — extended cold across the southern footprint forced controlled rotating outages, the first in SPP's history. Spring brings violent severe weather (tornadoes, large hail, damaging straight-line winds) that test grid hardening, and summer extreme heat across Oklahoma and Kansas regularly exceeds 100°F for extended stretches. The April 2026 western expansion adds high-altitude weather variability — Chinook downsloping winds along the Front Range, intense thunderstorms, and rapid snowmelt cycles. Hailstones large enough to damage solar panels are a regular spring and summer concern.

Question 4

How does the Storm Prediction Center warn for severe weather across SPP?

Accepted Answer

The Storm Prediction Center publishes daily convective outlooks (Marginal, Slight, Enhanced, Moderate, and High Risk) covering days 1 through 8, flagging areas where severe thunderstorms, tornadoes, and damaging winds are likely. Across the SPP footprint — the heart of Tornado Alley — Moderate and High Risk days drive the most aggressive grid-hardening posture. Tornado Watches typically precede Tornado Warnings, which are real-time alerts based on radar-detected rotation or trained spotter reports, and they routinely interrupt transmission and distribution operations across Kansas, Oklahoma, and the Texas Panhandle.

Question 5

What weather drives the SPP footprint's coldest emergency events?

Accepted Answer

Arctic air masses spilling south out of central Canada drive the most extreme cold across SPP. The Climate Prediction Center 6–10 and 8–14 day outlooks often signal these events a week or more in advance, followed by Wind Chill Watches and Warnings as the airmass approaches. Wind Chill Warning criteria across the northern footprint are typically -35°F or lower; across Oklahoma and Kansas the threshold is closer to -10°F. The February 2021 Winter Storm Uri event produced sustained sub-zero conditions across the entire SPP footprint and is the modern reference case.

Question 6

How are large-hail events tracked across the central plains?

Accepted Answer

Large hail (one inch or greater) is one of the most common severe-weather threats across SPP, and the SPC explicitly forecasts hail probability in its convective outlooks. Severe Thunderstorm Warnings are issued in real time when radar or spotter reports confirm hail of one inch or greater. Hailstones of 1.75 inches and up — often called 'significant severe' — are a particular concern for the rapidly growing utility-scale solar fleet across Oklahoma, Kansas, and the new Colorado footprint.

Question 7

What weather alerts dominate the new Colorado SPP footprint?

Accepted Answer

The Colorado Front Range adds high-altitude weather variability to SPP. The NWS issues High Wind Warnings for Chinook downsloping events along the Front Range that can produce gusts above 75 mph, Winter Storm Warnings and Blizzard Warnings for upslope snow, and Red Flag Warnings during the dry, windy transitions of spring and fall. Wildfire smoke from regional fires can also degrade solar output across the Colorado and southeastern Wyoming portions of the footprint for days at a time.

Question 8

How do Heat Advisories and Excessive Heat Warnings work across SPP?

Accepted Answer

The NWS issues Heat Advisories when forecast heat indices reach 100°F to 105°F for two or more hours and Excessive Heat Warnings at 105°F to 110°F or higher, with thresholds varying by climate zone. Across the central and southern SPP footprint — Oklahoma City, Tulsa, Wichita, Kansas City — these alerts are routine through July and August. Multi-day heat events with overnight lows in the 80s drive the highest summer cooling demand across the system.

Question 9

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

Accepted Answer

Specific event references on this page (the February 2021 Winter Storm Uri rotating outages and the April 2026 western footprint expansion) are drawn from the FERC, NERC, and Regional Entity Joint Inquiry into the February 2021 Cold Weather Event, SPP's Winter Storm Uri Comprehensive Report and integration filings at spp.org, and the NWS Storm Prediction Center convective outlook documentation at spc.noaa.gov.

Metric	Actual	Normal	Departure
CDD	739.9	524.5	+215.4
HDD	2370.1	2836.2	-466.1

SPP

Temperature Forecast

Precipitation Chance

Recent History (7 days)

SPP (Southwest Power Pool) — Frequently Asked Questions

All Sources for SPP