The county-level homework for Union County, South Dakota — its 461 square miles, its 4 ZIP codes, its place inside the Sioux City metro's coverage. TempReach USA connects homeowners here with independent local HVAC technicians; the record behind the routing is on this page.
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In brief: 461 square miles of South Dakota, a climate read from SIOUX CITY GATEWAY AP, IA US's normals, and a heating pressure as the county's dominant one — 6,860 heating degree days set against 866 cooling degree days in an average year. TempReach USA does not do the work itself; it is a referral service, and one call connects you with an independent local HVAC technician serving Union County.
The station for this county's metro is SIOUX CITY GATEWAY AP, IA US, and its NOAA 1991-2020 normals are the source of every figure in this section. Precipitation averages 29.27 inches a year; the temperature record averages 48.5 degrees, built from 24.6 days at 90 or above and 154.1 nights at or below freezing; the workload totals 6,860 heating degree days and 866 cooling degree days. Union County is read through that record throughout this page.
There is a housing arithmetic under Union County's heating season. The metro it belongs to built its largest share of homes before 1960 — 46.6% of the stock — with the next share between 1960 and 1979 at 23.5%, around a median build year of 1964. Fitted into those eras, the county's furnaces and heat pumps meet 154.1 freezing nights at very different ages, and the heating diary divides accordingly: deep repair conversations in the older bands, first-replacement conversations in the newer ones.
Set the county inside its metro and the picture completes. Union County answers to the Sioux City metro's data — its housing profile, its problem ranking, its climate station — but the county is where that data touches ground: 5 communities, 4 ZIP codes, one county's worth of systems ageing under the record kept at SIOUX CITY GATEWAY AP, IA US. This page is that ground-level reading, kept separate from the metro page so the local detail is never averaged away.
There is a scale fact hidden in Union County's ZIP codes: 4 codes across 461 square miles works out to 115.2 square miles per code, which makes a service call here a matter of ground as well as of systems. The codes on the metro-facing side of the county — the county sits northwest of the Sioux City metro's centre — and the codes at its far edge hold different ground, but both ends ask the same climate questions of their heating and cooling, at different distances.
Read the map around Union County and a working region appears: Dakota County, Woodbury County are the neighbouring names at the head of its list of 2, and together these counties form the ground a local technician actually covers. The county line decides which page describes a home; it does not decide the weather the home's system faces, the decade its street was built in, or the season its diary fills. Those are regional — and the region, on this site, is a set of county pages that link to one another, as the cards below do.
Two numbers organise Union County's heating and cooling year: 6,860 and 866, the heating and cooling degree days in the normals at SIOUX CITY GATEWAY AP, IA US. Whichever runs larger decides the county's dominant pressure — here, a heating one — and with it the season a household should prepare for first. The supporting figures fill in the texture: 48.5 degrees as the year's average temperature, 24.6 hot days, 154.1 freezing nights, 29.27 inches of precipitation. Every paragraph on this page is, in the end, a reading of those six numbers on this county's ground.
The county's place list tells its own story. Dakota Dunes (4,129 residents) is the largest of the 5 communities the record names for Union County, with North Sioux City (3,018 residents) behind it and Elk Point and Alcester further down the list. A technician working this county works all of those places in a single week, and the systems change character with the address: the era a community was built in decides whether the call is about an ageing furnace, a condenser at the end of its summers, or ductwork that predates the equipment it now serves.
Spread the metro's eras over Union County's own ground and the housing paragraph becomes a map: 461 square miles, 4 ZIP codes at 115.2 square miles per code, and a stock whose largest band was built before 1960 (46.6%), whose pre-1980 share runs to 70.1% and whose post-2000 share runs to 14.4%. The percentages are the metro's; the streets they land on are this county's, and a technician driving from one end of the county to the other drives through the bands in sequence.
One way to hold Union County in mind is as the local layer of a wider dataset. Above it sits the Sioux City metro, with its Census housing profile and its NOAA station at SIOUX CITY GATEWAY AP, IA US. At this level sit the county's own numbers — 461 square miles, 2 neighbouring counties, 4 ZIP codes, 5 listed places — and below it, not published anywhere, sit the individual homes whose systems all of it describes. This page works at the middle level, where the data is still local enough to act on.
City pages carry the metro-wide homework — housing eras, the problem ranking, services in depth. This county sits inside their coverage.
Population 4,129
Population 3,018
Population 2,391
Population 987
Population 717
TempReach USA is not an HVAC company. We employ no heating or cooling technicians, we run no service trucks, and we do not carry out HVAC work of any kind. This website and its call center exist for one purpose: to connect homeowners with independent local heating and cooling professionals who serve their area. When you call the number on this site, your call is routed to such a professional. From that point, everything about the job belongs to that professional and to you: the assessment, the work itself, the scheduling, what you are charged, and the terms of any agreement you reach. The professional who takes your job is solely responsible for it. The technician who arrives at your home runs their own business; they are not an employee, agent or subcontractor of TempReach USA. Our part is the information on these pages — assembled from Census Bureau housing data and NOAA climate records for each metro — and the routing of your call. We state this plainly on purpose: you should know exactly who you are hiring before anyone picks up a wrench or a gauge.
One call connects you with an independent local heating and cooling professional serving Union County and the Sioux City metro.
Call center hours: Mon-Fri 7:00 AM-10:00 PM ET | Sat 8:00 AM-10:00 PM ET | Sun 7:00 AM-9:00 PM ET