Updated MAR 2023/JAN 2025/MAR 2026/SEP 2026
The purpose of this post is to catalogue counts of monthly record high maxes, high minimums, low maxes and low minimums coming into the National Centers for Environmental Information’s site and all related charts and graphs produced in my Excel files for Canadian data sets. Monthly records are those set for the entire period of one month. For example, the highest temperature set during the month of March at Atlanta Hartsville-Jackson International Airport was 89F set on 3/23/1995. I am in the process of constantly updating this data verifying the 2009 Meehl et al. surface records study published in Geophysical Research Letters that I initiated from 2009. Each individual count could be a tied surface record or one broken by several degrees Fahrenheit.
Here is the link to the NCEI site:
https://www.ncdc.noaa.gov/cdo-web/datatools/records
More from NCEI:
“The daily records summarized here are compiled from a subset of stations in the Global Historical Climatological Network. A station is defined as the complete daily weather records at a particular location, having a unique identifier in the GHCN-Daily dataset.
For a station to be considered for any parameter, it must have a minimum of 30 years of data with more than 182 days complete each year. This is effectively a “30-year record of service” requirement, but allows for inclusion of some stations which routinely shut down during certain seasons. Small station moves, such as a move from one property to an adjacent property, may occur within a station history. However, larger moves, such as a station moving from downtown to the city airport, generally result in the commissioning of a new station identifier. This tool treats each of these histories as a different station. In this way, it does not “thread” the separate histories into one record for a city.
This tool provides simplistic counts of records to provide insight into recent climate behavior, but is not a definitive way to identify trends in the number of records set over time. This is particularly true outside the United States, where the number of records may be strongly influenced by station density from country to country and from year to year. These data are raw and have not been assessed for the effects of changing station instrumentation and time of observation.”
An updated 2016 study from Dr. Jerry Meehl indicates that the daily ratio from year to year will average around 15 to 1 by 2100:
Per one of the authors of both the 2009 and 2016 studies, Claudia Tebaldi said “This climate is on a trajectory that goes somewhere we’ve never been. And records are a very easy measure of that.”
All of the data listed below is part of this one chart. The ratio of monthly record high maxes to low minimums for the 2020s (so far) is higher than any decade since the 1900s:
Here are the current Canadian monthly record counts per decade (including ties):
Canada MHMX/MLMN Monthly Record Analysis
This file compares Canadian monthly record high maximum temperatures (MHMX) with monthly record low minimum temperatures (MLMN) in relation to Canada’s national monthly temperature anomaly.
The analysis covers January 1901 through December 2025 and groups each month into 0.10°C anomaly bins relative to the 1961–1990 Canadian climatological baseline. For every anomaly bin, the workbook totals the number of MHMX and MLMN records occurring during all months that fell within that temperature range.
The purpose is to examine how the balance between unusually warm and unusually cold monthly temperature records changes as Canada’s overall monthly temperature moves progressively farther above or below normal.
The chart titled “Canada Signed MHMX/MLMN Comparison vs Temperature Anomaly” displays that relationship. Each row represents a 0.10°C national temperature-anomaly interval. The accompanying columns show the total MHMX records, total MLMN records, the number of months represented in the bin, the signed comparison ratio, the anomaly-bin midpoint, and the square-root-scaled value used for plotting.
Positive values indicate that monthly record high maximum temperatures outnumber monthly record low minimum temperatures, while negative values indicate that monthly record low minimum temperatures dominate. The warm side of the comparison is shown in red and the cold side in blue.
Because some of the most extreme warm and cold anomaly bins contain only one or a few months, very large ratios in the tails should be interpreted cautiously. The important result is the broader progression across the well-populated part of the distribution.
That progression is clear. During strongly negative Canadian temperature anomalies, MLMN records generally dominate. As anomalies approach the 1961–1990 climatological mean, the imbalance diminishes and the two record types become much more competitive. Once anomalies become positive, MHMX records increasingly dominate, and that warm-record advantage grows substantially as the national monthly anomaly rises.
For example, near +0.5°C, the warm side already has a clear advantage. By roughly +1.5°C, the imbalance toward MHMX records becomes much stronger, and many bins above about +2°C to +3°C show large warm-to-cold ratios. Conversely, many bins several degrees below normal show a pronounced dominance of MLMN records.
The final Signed √ Ratio column applies a square-root transformation to the magnitude of the signed ratio. This keeps very large warm or cold ratios from overwhelming the graphic while preserving both the direction and relative strength of the imbalance.
Taken as a whole, this chart demonstrates a strong statistical relationship between the background monthly temperature of Canada and the type of monthly temperature record most likely to occur. Colder-than-normal months favor cold monthly records, while warmer-than-normal months increasingly favor warm monthly records. The farther the national temperature moves toward the warm side of the climatological distribution, the more strongly the record balance shifts toward MHMX.
As with the Canadian daily-record analysis, this should be interpreted as an observed statistical association rather than a formal attribution calculation. Individual monthly records can be affected by weather variability, geography, station coverage, instrumentation, and the number of observations available. The scientific value lies in the systematic change in the relative frequency of warm versus cold monthly records across the national temperature-anomaly spectrum.
The 2020s:
In the following charts blue colors represent cold months and years, and red warm. Those months with counts close to a 1 to 1 ratio of highs to lows are colored black. All-time record hot and cold months and years are colored purple. I have opted not to catalogue data prior to 1890 since record counts decrease substantially prior to that year. Time stamps for when I last updated counts are located in the upper left-hand corner of each chart. Drop me a note if you see an error or if you have suggestions for improvements.
The 2010s:
The 2000s:
The 1990s:
The 1980s:
The 1970s:
The 1960s:
The 1950s:
The 1940s:
The 1930s:
The 1920s:
The 1910s:
The 1900s:
All of the data listed below is part of this one chart. The ratio of monthly record high minimums to low maximums for the 2010s (so far) is higher than any other decade since the 1900s:
Here are the current monthly record counts per decade:
Canada MHMN/MLMX Monthly Record Analysis
This file compares Canadian monthly record high minimum temperatures (MHMN) with monthly record low maximum temperatures (MLMX) in relation to Canada’s national monthly temperature anomaly.
The analysis covers January 1901 through December 2025 and places each month into 0.10°C anomaly bins relative to the 1961–1990 Canadian climatological baseline. The workbook then totals the MHMN and MLMX records occurring during all months assigned to each anomaly interval. The file itself notes that 2026 record counts are excluded because that year is incomplete.
The purpose is to examine how the balance between exceptionally warm monthly minimum temperatures and exceptionally cold monthly maximum temperatures changes as Canada’s overall monthly temperature moves farther above or below its long-term climatological average.
The chart comparing MHMN with MLMX versus temperature anomaly is especially useful because these two record categories describe opposite ends of an important aspect of the temperature distribution. MHMN records occur when a month’s minimum temperature is unusually high, indicating exceptional warmth on the cool side of the monthly temperature range. MLMX records occur when a month’s maximum temperature is unusually low, representing months in which even the daytime or warm side of the temperature distribution remains exceptionally cold.
For each 0.10°C anomaly bin, the chart compares the accumulated MHMN and MLMX record counts and calculates a signed ratio showing which record category dominates. Positive values indicate that MHMN records outnumber MLMX records, while negative values indicate that MLMX records are more numerous. Warm-dominant values are shown on the positive side of the comparison and cold-dominant values on the negative side.
A square-root transformation is then applied to the magnitude of the signed ratio. This prevents a few very large ratios in sparsely populated extreme anomaly bins from overwhelming the chart visually while retaining both the direction and relative strength of the warm-versus-cold imbalance.
The broad relationship is the important feature of the analysis. During months with strongly negative national temperature anomalies, monthly record low maximums tend to dominate, reflecting conditions in which even the warmest portions of the monthly temperature cycle remain unusually cold. As anomalies approach the 1961–1990 climatological mean, the difference between the two categories diminishes.
Once Canadian monthly temperatures move into positive anomaly territory, the relationship increasingly shifts toward record high minimum temperatures. As national monthly anomalies become progressively warmer, MHMN records become much more common relative to MLMX records. This represents an increasing tendency for the normally cooler portion of the monthly temperature distribution to remain unusually warm while exceptionally cold monthly maximum temperatures become less frequent.
This comparison is particularly informative because it provides a measure of changes in the lower and upper boundaries of monthly temperature behavior. Increasing MHMN dominance indicates that unusually warm minimum temperatures are becoming increasingly prevalent under warm background conditions, while decreasing MLMX frequency indicates that exceptionally cold monthly daytime conditions become progressively less common.
The chart therefore does more than count warm and cold records. It shows how the balance between monthly record warmth and monthly record cold changes systematically with Canada’s background temperature anomaly. Cold anomalies favor MLMX records, conditions near normal produce much more balanced record frequencies, and increasingly positive anomalies favor MHMN records by progressively larger margins.
As with the other Canadian record analyses, very large ratios in the extreme warm or cold tails should be interpreted cautiously because some anomaly bins contain only one or a few months. The more scientifically meaningful feature is the consistent progression across the well-populated portion of the anomaly distribution.
This should also be interpreted as an observed statistical association rather than a formal attribution analysis. Individual monthly records depend on weather patterns, geography, station availability, instrumentation, and other observational factors. The important result is the systematic change in the relative frequency of record high monthly minimums versus record low monthly maximums as Canada’s national temperature anomaly changes.
The 2020s:
In the following charts blue colors represent cold months and years, and red warm. Those months with counts close to a 1 to 1 ratio of highs to lows are colored black. Purple colors represent hottest and coldest months and years. I have opted not to catalogue data prior to 1890 since record counts decrease substantially prior to that year. Time stamps for when I last updated counts are located in the upper left-hand corner of each chart. Drop me a note if you see an error or if you have suggestions for improvements.
The 2010s:
The 2000s:
The 1990s:
The 1980s:
The 1970s:
The 1960s:
The 1950s:
The 1940s:
The 1930s:
The 1920s:
The 1910s:
1900s:
These are the counts of Canadian monthly record reports in the NCEI database going back to 1900.
Guy Walton…”The Climate Guy”