Mid-February 2021 unleashed a relentless blast of brutal cold, the likes of which South Central Nebraska had not endured in several decades. For the majority of the 24-county area, the 10-day stretch from the 7th-16th marked the overall-coldest 10 days in nearly 38 years...since December 1983 (based on average/mean temperature). In addition to various other official NWS stations (including both automated airport sensors and cooperative observers), this fact rang true for Grand Island and Hastings airports, where the 10-day average temperature from the 7th-16th was -4.7 and -5.5 degrees (F), respectively. Following are various other cold temperature tidbits specifically for Grand Island (126 years of temperature records) and Hastings (114 years of records), although very similar realities applied elsewhere within South Central Nebraska. At Grand Island, the average temperature between the 7th-16th was an incredible 33 degrees below the 30-year normal, as daily highs over the course of the 10 days ranged from -7 to +10, while daily lows ranged from -27 to +1. Furthermore, Grand Island notched nine straight days of sub-zero lows between the 8th-16th (longest such streak since Dec. 1989), and both Grand Island and Hastings spent OVER 60-CONSECUTIVE HOURS BELOW ZERO between the early morning of the 14th and the afternoon/evening of the 16th (had not happened since at least Feb. 1989). At Hastings, the high temperature of -8 on the 15th set a new February record for coldest daily high and was only one-degree short of the record-coldest high (for any month) of -9 set in Dec. 1989. Perhaps most impressively, Hastings plunged to -30 for the low on the 16th, tying its all-time coldest reading first observed way back in Jan. 1912. A few long-time NWS coop observer stations actually set outright all-time coldest low temperatures on the 16th, including York (-34), Superior (-33) and Osceola (-31). Greeley and Ord airport (ASOS) matched the York reading of -34 for the outright-coldest official temperature of this particular cold snap. Factoring in winds (albeit relatively light through the majority of the 10-day period), the most frigid wind chill readings occurred between the evening of the 14th and the morning of the 16th, prompting a long-fuse Wind Chill Warning for all of South Central Nebraska. On both mornings of the 15th and 16th, dozens of automated stations (official and unofficial) recorded wind chill values well down into the -30 to -45 range, and even a few that breached -50. While each morning registered fairly similar and dangerously-cold values area-wide, the morning of the 15th featured both the coldest known official wind chill (-54 at Ord airport ASOS) and unofficial wind chill (-55 from a NDOT sensor two miles south of Elm Creek).
Focusing on impacts, the local South Central Nebraska area was just a small portion of an expansive swath of the central and southern United States that battled this historic cold, as sub-freezing temperatures surged all the way into south Texas (even promoting a light coating of snow at Galveston). This cold outbreak put a considerable strain on not only the local, but especially the regional power and energy industry. While South Central Nebraska avoided more serious/longer-lasting power disruptions that ravaged many southern states, fairly brief rolling blackouts (typically around 30 minutes) occurred within the area on the 15th-16th, as called for by the Southwest Power Pool (the independent regional transmission organization that manages the electric grid and wholesale power market for portions of 14 central and southern states, including Nebraska). Turning to the large-scale meteorological picture, this prolonged/intense cold outbreak was driven in the mid-upper levels by a parade of troughs circulating around a quasi-stationary parent vortex churning over southern Canada, each one further reinforcing/intensifying the magnitude of Arctic air allowed to spill southward through the central United States. At the surface, persistent, predominantly northerly flow prevailed for days on end as a sprawling Arctic high increasingly-dominated much of the central and northeastern United States. Also contributing to the magnitude of persistent cold in South Central Nebraska was increasingly-deep snow cover, as a series of snow events gradually boosted the average snow depth across the area from generally 2-5 inches on the 5th (just prior to the onset of the Arctic outbreak) to a widespread 10-15 inches by the 15th-16th (during the heart of the very-coldest readings). Concluding with a brief rundown of how South Central Nebraska finally crawled out from underneath the 10-day crush of ruthless cold, improvement finally got underway on the 17th and trended upward for several days thereafter, with high temperatures at Grand Island/Hastings recovering into the teens on the 17th, 20s on the 18th-19th, 30s on the 20th-21st (ending a 15-day sub-freezing streak), 40s on the 22nd and finally into the 50s on the 23rd (some parts of South Central Nebraska even reached the 60s that day).