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USA Climate: State Index

Average weather charts for USA states and territories, 8713 locations to choose from. Most show precipitation, high and low temperatures, and degree-days, others have only precipitation. The charts make it easy to see how climate for a particular location changes over the year, and how climate varies between locations.

Scroll down for explanation and discussion.

Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Pacific Islands
Puerto Rico
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Virgin Islands
Washington
Washington, D.C.
West Virginia
Wisconsin
Wyoming

About the USA Charts

The Data      Daylight      Frost Dates      Rankings      Degree Days      Suggestions

90% of the USA Charts are based on National Oceanic and Atmospheric Administration (NOAA) data. These are sometimes referred to as Series 2 in this site. The discussion below applies to them. The rest of the USA Charts (and all of the World charts) are based on data from the World Meteorological Organization. These are sometimes referred to as Series 1 in this site. See About the World Charts for more info about them.

All of the charts have the same scales, which makes it easy to compare different stations. The scales fit the extremes of the USA data, although the temperatures sneak off the top or bottom of the range for a few stations.

The latitude, longitude, and elevation of each location are also shown at the top of the chart, along with the NOAA station ID.

The month columns are spaced according to the number of days in the month, although that is hard to see. Seasons are shown with a background color.

I make the charts with a series of hand-written software tools. I embed the NOAA data in PostScript language files, then use ImageMagick to create the .png images shown here.

The Data

Almost all of the data is from NOAA U.S. Daily Climate Normals 1971-2000. These come from 7937 weather stations all over the USA. Some stations show only precipitation, but most also show high and low temperatures and heating and cooling degree days.

The frost date/percentage data is from another NOAA page: Freeze/Frost Data, CLIM20 supplement #1

Data Geeks: Even over 30 years, the daily records have too much variation to show smooth changes. One bad storm or cold spell could put a spike in the curve. So, NOAA uses mathematical techniques applied to monthly data to produce the smooth daily data shown here. I haven't done any further processing, the values here are exactly as provided by NOAA.

Sunrise, Sunset, and Daylight

The sunrise and sunset times shown in the charts are approximate. They are accurate for the latitude, and show the precise amount of daylight, but the rise and set times may be offset (up or down in the chart) because time zones and daylight savings time are not considered. The charts are made assuming that the location is in the middle of an evenly spaced time zone.

For precise times see US Naval Observatory. Along with latitude and longitude, which are shown on each page, you'll also need the time zone.

The sunrise/set charts don't say anything about sunniness or cloudiness, just when the sun up or down.

Frost Dates

A majority of USA stations have freeze/frost data. The percentages indicate how likely it is that a frost will occur.

For autumn the percentages show the likelihood of the first frost before the the given date. For example, a 10% value for September 30th means that there is a 10% chance that there will be a frost before that date. This is the same as saying there is a 90% chance that the first frost of the year will occur on or after that date.

For spring the percentages show the likelihood of that the last frost before the given date. For example, a 90% value for March 1 means that there is a 90% chance that there will be no more frost after this. In other words there is only a 10% chance that another frost will occur that year.

For some warm locations, the before and after dates are close together and may occur in the same season, usually winter.

Rankings & Extremes

Rankings are based on annual averages. Not every station reports every statistic, so the rankings are based only on those that do report. For example, if a station doesn't report high temperature, it is not ranked for that.

Well add some ranking lists to these pages in the near future.

Heating and Cooling Degree Days

These are derived from the temperature data. Simply put, they show how hard your furnace or air conditioner has to work to maintain a comfortable interior temperature. See the Wikipedia entry for more detail.

Suggestions?

Please let me know if you have any problems, questions, comments, or suggestions.

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