# Understanding NOAA’s monthly climate outlooks

## Outlook schedule

On the third Thursday of every month, NOAA’s Climate Prediction Center issues an outlook for temperature and precipitation for the United States for the coming month. These outlooks are updated on the last day of each month. Those updated outlooks are the basis for the posts that appear on Climate.gov each month.

*Outlooks* are not the same as weather *forecasts*

Most people understand a *forecast* to be a prediction of the high (or low) temperature or precipitation amount likely to occur on a given day. NOAA’s monthly and seasonal outlooks do not predict specific monthly (or seasonal) temperatures or precipitation amounts. Instead, they try to predict which of three possible outcomes is most likely to occur: above-average, near-average, or below-average monthly mean temperature or total precipitation.

To qualify as ** above** or

*below**, the Climate Prediction Center requires the monthly temperature or precipitation to be in the upper or lower one-third of values observed from 1991-2020 for a given month. To distinguish this definition from the more literal definition, we often describe the categories as “well above (or below) average,” or sometimes “much wetter (or drier) than average”. If forecasters think all three possible temperature or precipitation outcomes (above-, near-, and below-average) are equally likely, or have no basis for selecting one category over the others, they issue an “equal chances” forecast.*

**average**## About the maps

### White areas do not mean average

White areas mean "equal chances". In those areas, forecasters think that all three possible monthly temperature or precipitation categories are equally likely. In other words, the chances of a warmer-than-average month are the same as the chances of a near-average or a cooler-than-average month.

### Blue areas

Blue areas mean a much cooler than average month is more likely than a near-average or a much warmer than average month. Darker blues mean higher chances of a relatively cold (lowest one-third) month—not increasingly extreme cold.

### Orange/red areas

Orange to red areas mean a much warmer than average month is more likely than a near-average or a much cooler than average month. Darker reds mean higher chances of a relatively (highest one-third) warm month—not increasingly extreme heat.

### Green areas

Green areas mean a much wetter than average month is more likely than a near-average or a much drier than average month. Darker greens mean higher chances of a relatively (highest one-third) wet month—not increasingly wetter conditions.

### Brown areas

Brown areas mean a much drier than average month is more likely than a near-average or a much wetter than average month. Darker greens mean higher chances of a relatively (lowest one-third) dry month—not increasingly drier conditions.

## Outlook math

In contrast to the “equal chances” forecast, sometimes things are happening in the climate system that tilt the odds toward or away from the default climatological frequency (an equal 33.3 percent chance for each outcome). When that happens, forecasters subtract the most likely probability (for example, a 60 percent chance of above-average temperatures) from 100 percent and divide the probability of the other two categories over the remainder (40 percent).

The remaining probabilities (40 percent in our example) are not just split evenly between the two remaining categories, however (near- and below-average temperatures). Physically speaking, it makes sense that if the odds have tilted *toward* one extreme climate outcome by a given percent, they’ve tilted *away* from the opposite extreme outcome by an equal amount. So by convention, forecasters divvy up the remaining probability by holding the chances for near-normal conditions at the “default” 33.3 percent, and then subtracting that from the total remainder (40-33.3). What’s left (6.7 percent) is the probability of the less-favored category.

When the odds of one climate outcome are so high (more than 63.3 percent) that the remaining fraction is smaller than 36.7 percent, forecasters set a minimum 3.3 percent chance for the opposite outcome, with the remainder being the probability of a near-normal outcome. (The least favored category never decreases below 3.3%, as there’s always some degree of uncertainty in any climate forecast and always some small chance of a surprise outcome).

## Seeing what static maps don’t show

In the real world, the probability for a single category will never be 100 percent. We will never be able to say a month in advance that there is a 100 percent chance of a wetter-than-average May, for instance. The climate is not that predictable. The full monthly climate outlook, then, will always include three separate probabilities for each location.

But only one color can be shown on a static map, so forecasters show the color of the most likely category—red and blue for above- or below-normal temperature, green or brown for above- or below-normal precipitation. It’s easy to mistake that single color for a specific forecast, and to not realize that that the other outcomes remain possible.

If you’d like a more complete picture of the monthly climate outlook, the Climate Prediction Center offers an interactive map that allows users to see the full suite of probabilities for a given location.

## Links