Record envelope, standing records and threshold days for East Helena (USC00242634), Montana, United States, with 34 years of record.
Key Facts for East Helena
East Helena (USC00242634) is a weather station in Montana, United States at 46.58 latitude and -111.92 longitude, 1,189 m (3,901 ft) above sea level.
The station reports from 1925 to 1958, 34 years of record.
1,464 records set at East Helena still stand.
Records are tracked for tmax, tmin, prcp: an element needs 30 years of data to be eligible.
East Helena set a daily record precipitation of 3.3 mm (0.13 in) on 14 February 1958.
About the Station
Location: Montana, United States, 46.58 latitude, -111.92 longitude.
Elevation: 1,189 m (3,901 ft).
Period of record: 1925 to 1958, 34 years.
Eligible elements: tmax, tmin, prcp.
Daily Record Envelope and 2026
0 days at or beyond a record
Record highRecord low2026 daily maximum2026 daily minimum
The band shows the record high and record low for each calendar day at East Helena. The lines show the 2026 daily maximum and minimum. 0 days in 2026 matched or passed a record. Temperatures are in degrees Celsius.
Daily record high and record low at East Helena, with 2026 drawn through them
Month
Highest record high
Lowest record low
2026 highest maximum
2026 lowest minimum
Jan
15.6 C (60.1 F)
-40.6 C (-41.1 F)
n/a
n/a
Feb
21.7 C (71.1 F)
-42.8 C (-45.0 F)
n/a
n/a
Mar
23.3 C (73.9 F)
-35.0 C (-31.0 F)
n/a
n/a
Apr
31.1 C (88.0 F)
-24.4 C (-11.9 F)
n/a
n/a
May
35.0 C (95.0 F)
-8.3 C (17.1 F)
n/a
n/a
Jun
38.3 C (100.9 F)
0.0 C (32.0 F)
n/a
n/a
Jul
40.0 C (104.0 F)
2.8 C (37.0 F)
n/a
n/a
Aug
40.6 C (105.1 F)
1.7 C (35.1 F)
n/a
n/a
Sep
36.7 C (98.1 F)
-13.9 C (7.0 F)
n/a
n/a
Oct
28.9 C (84.0 F)
-22.2 C (-8.0 F)
n/a
n/a
Nov
23.3 C (73.9 F)
-31.7 C (-25.1 F)
n/a
n/a
Dec
18.3 C (64.9 F)
-38.3 C (-36.9 F)
n/a
n/a
Which Years Hold Standing Records
1,464 standing records
Year with most
1,464 records at East Helena still stand. 1936 holds the most, with 103.
Standing records at East Helena by the year they were set
Year set
Standing records
1925
63
1926
64
1927
35
1928
44
1929
41
1930
48
1931
48
1932
63
1933
54
1934
55
1935
42
1936
103
1937
40
1938
38
1939
55
1940
44
1941
35
1942
45
1943
41
1944
31
1945
25
1946
26
1947
27
1948
26
1949
45
1950
46
1951
46
1952
27
1953
49
1954
45
1955
52
1956
30
1957
30
1958
1
All-Time Record Progression
1 new records
1 all-time records were set at East Helena between 26 January 1957 and 26 January 1957. Each dot is a new record.
When East Helena set new all-time records
Date
Kind
Detail
1957-01-26
Record low maximum temperature
Record low maximum temperature -30.6 C (-23.1 F)
Wettest Day of Each Month
Aug: 65.0 mm (2.6 in)
The wettest day on record for each calendar month at East Helena. The most was 65.0 mm (2.6 in) on 21 August 1933.
Record daily precipitation for each month at East Helena
Month
Record daily precipitation (mm)
Date
Jan
12.7 mm (0.5 in)
5 January 1937
Feb
10.7 mm (0.4 in)
12 February 1936
Mar
20.3 mm (0.8 in)
4 March 1935
Apr
23.6 mm (0.9 in)
30 April 1951
May
39.6 mm (1.6 in)
8 May 1948
Jun
52.1 mm (2.1 in)
9 June 1947
Jul
27.2 mm (1.1 in)
18 July 1955
Aug
65.0 mm (2.6 in)
21 August 1933
Sep
54.4 mm (2.1 in)
26 September 1947
Oct
15.7 mm (0.6 in)
23 October 1954
Nov
14.2 mm (0.6 in)
5 November 1927
Dec
15.5 mm (0.6 in)
13 December 1937
Period of Record Coverage
1925 to 1958
Complete yearUnder 90 percent of days
34 years of record at East Helena, 1925 to 1958. 1 years have data for under 90 percent of days and are left out of rankings: 1958.
Cooler than the station meanWarmer than the station mean
One stripe for each of 32 complete years at East Helena, 1925 to 1957. Blue stripes are years cooler than the station's own mean of 6.5 C (43.7 F); red stripes are warmer. The coolest year was 1951, at 4.5 C (40.1 F), and the warmest was 1934, at 8.9 C (47.9 F). The strongest colour marks a difference of 2.4 C (4.3 F).
Annual mean temperature at East Helena as warming stripes, 1925 to 1957
Year
Annual mean temperature
Difference from the station mean
1925
7.7 C
+1.20 C
1926
7.6 C
+1.12 C
1927
5.6 C
-0.95 C
1928
6.3 C
-0.22 C
1929
5.3 C
-1.20 C
1930
6.5 C
-0.01 C
1931
7.5 C
+1.03 C
1932
6.6 C
+0.05 C
1933
7.5 C
+0.99 C
1934
8.9 C
+2.35 C
1935
6.3 C
-0.21 C
1936
6.1 C
-0.37 C
1937
6.1 C
-0.44 C
1938
6.9 C
+0.43 C
1939
7.8 C
+1.34 C
1940
7.2 C
+0.73 C
1941
7.1 C
+0.63 C
1942
5.4 C
-1.11 C
1943
5.9 C
-0.65 C
1944
5.9 C
-0.57 C
1945
6.9 C
+0.39 C
1946
7.6 C
+1.09 C
1948
6.0 C
-0.53 C
1949
5.6 C
-0.88 C
1950
5.3 C
-1.23 C
1951
4.5 C
-2.00 C
1952
6.2 C
-0.32 C
1953
8.6 C
+2.06 C
1954
6.6 C
+0.07 C
1955
4.9 C
-1.56 C
1956
6.4 C
-0.15 C
1957
5.4 C
-1.14 C
The fitted trend in annual mean temperature here over 1925 to 1957 is -0.34 C (-0.72 to 0.04) per decade. The interval includes zero, so the trend is not clearly different from zero. In Fahrenheit: -0.6 F (-1.3 to 0.1) per decade. The slope is a straight line fitted to 32 complete years; the brackets give its 95 percent interval.
Fitted temperature trends per decade at East Helena
Measure
Per decade (C)
Per decade (F)
Period
Complete years
Reading
Annual mean temperature
-0.34 C (-0.72 to 0.04) per decade
-0.6 F (-1.3 to 0.1) per decade
1925 to 1957
32
Not clearly different from zero
Mean daily maximum
-0.2 C (-0.7 to 0.2) per decade
-0.4 F (-1.2 to 0.3) per decade
1925 to 1957
32
Not clearly different from zero
Mean daily minimum
-0.4 C (-0.8 to -0.1) per decade
-0.8 F (-1.5 to -0.1) per decade
1925 to 1957
32
Fall
A year is complete when all 12 months have at least 20 days of both daily maximum and daily minimum readings. The annual mean is the mean of the monthly means. The trend describes this one station over this period; it does not say what caused the change.
Extremes by Year
1925 to 1958
Yearly extremes at East Helena: the record and the median year
Measure
Record
Year of the record
Median year
Years with a value
Hottest day (TXx)
40.6 C (105.1 F)
1940
36.7 C (98.1 F)
34
Coldest night (TNn)
-42.8 C (-45.0 F)
1936
-34.4 C (-30.0 F)
34
Wettest day (Rx1day)
65.0 mm (2.6 in)
1933
24.0 mm (0.9 in)
32
Wettest five days (Rx5day)
81.5 mm (3.2 in)
1947
38.1 mm (1.5 in)
32
Longest dry spell (CDD)
60 days
1932
36 days
32
Hottest day (TXx)
The hottest day of the year at East Helena, 1925 to 1958. The record is 40.6 C (105.1 F) in 1940, marked on the chart; the median year is 36.7 C (98.1 F).
Hottest day (TXx) at East Helena by year
Year
Hottest day (TXx)
1925
37.8 C (100.0 F)
1926
36.1 C (97.0 F)
1927
33.9 C (93.0 F)
1928
38.3 C (100.9 F)
1929
39.4 C (102.9 F)
1930
37.2 C (99.0 F)
1931
40.0 C (104.0 F)
1932
36.7 C (98.1 F)
1933
38.9 C (102.0 F)
1934
39.4 C (102.9 F)
1935
39.4 C (102.9 F)
1936
40.0 C (104.0 F)
1937
39.4 C (102.9 F)
1938
35.0 C (95.0 F)
1939
37.2 C (99.0 F)
1940
40.6 C (105.1 F)
1941
37.2 C (99.0 F)
1942
36.7 C (98.1 F)
1943
34.4 C (93.9 F)
1944
33.9 C (93.0 F)
1945
35.0 C (95.0 F)
1946
36.7 C (98.1 F)
1947
36.1 C (97.0 F)
1948
35.0 C (95.0 F)
1949
38.9 C (102.0 F)
1950
36.7 C (98.1 F)
1951
36.1 C (97.0 F)
1952
36.1 C (97.0 F)
1953
39.4 C (102.9 F)
1954
37.2 C (99.0 F)
1955
36.7 C (98.1 F)
1956
35.0 C (95.0 F)
1957
36.7 C (98.1 F)
1958
12.8 C (55.0 F)
Coldest night (TNn)
The coldest night of the year at East Helena, 1925 to 1958. The record is -42.8 C (-45.0 F) in 1936, marked on the chart; the median year is -34.4 C (-30.0 F).
Coldest night (TNn) at East Helena by year
Year
Coldest night (TNn)
1925
-20.0 C (-4.0 F)
1926
-30.0 C (-22.0 F)
1927
-38.9 C (-38.0 F)
1928
-35.0 C (-31.0 F)
1929
-38.9 C (-38.0 F)
1930
-39.4 C (-38.9 F)
1931
-25.0 C (-13.0 F)
1932
-37.2 C (-35.0 F)
1933
-42.2 C (-44.0 F)
1934
-26.1 C (-15.0 F)
1935
-37.8 C (-36.0 F)
1936
-42.8 C (-45.0 F)
1937
-40.6 C (-41.1 F)
1938
-33.9 C (-29.0 F)
1939
-36.1 C (-33.0 F)
1940
-30.6 C (-23.1 F)
1941
-32.8 C (-27.0 F)
1942
-38.9 C (-38.0 F)
1943
-36.7 C (-34.1 F)
1944
-31.7 C (-25.1 F)
1945
-30.0 C (-22.0 F)
1946
-28.3 C (-18.9 F)
1947
-27.8 C (-18.0 F)
1948
-28.9 C (-20.0 F)
1949
-36.7 C (-34.1 F)
1950
-35.6 C (-32.1 F)
1951
-32.2 C (-26.0 F)
1952
-30.0 C (-22.0 F)
1953
-21.7 C (-7.1 F)
1954
-37.8 C (-36.0 F)
1955
-31.7 C (-25.1 F)
1956
-35.0 C (-31.0 F)
1957
-38.9 C (-38.0 F)
1958
-18.3 C (-0.9 F)
Wettest day (Rx1day)
The wettest day of the year at East Helena, 1925 to 1958. The record is 65.0 mm (2.6 in) in 1933, marked on the chart; the median year is 24.0 mm (0.9 in).
Wettest day (Rx1day) at East Helena by year
Year
Wettest day (Rx1day)
1925
n/a
1926
n/a
1927
29.7 mm (1.2 in)
1928
15.5 mm (0.6 in)
1929
13.0 mm (0.5 in)
1930
28.7 mm (1.1 in)
1931
15.2 mm (0.6 in)
1932
26.7 mm (1.1 in)
1933
65.0 mm (2.6 in)
1934
21.8 mm (0.9 in)
1935
20.3 mm (0.8 in)
1936
17.0 mm (0.7 in)
1937
30.7 mm (1.2 in)
1938
18.3 mm (0.7 in)
1939
12.7 mm (0.5 in)
1940
23.9 mm (0.9 in)
1941
31.8 mm (1.3 in)
1942
20.6 mm (0.8 in)
1943
41.9 mm (1.6 in)
1944
25.4 mm (1.0 in)
1945
20.6 mm (0.8 in)
1946
25.4 mm (1.0 in)
1947
54.4 mm (2.1 in)
1948
39.6 mm (1.6 in)
1949
24.1 mm (0.9 in)
1950
18.3 mm (0.7 in)
1951
23.6 mm (0.9 in)
1952
19.1 mm (0.8 in)
1953
38.1 mm (1.5 in)
1954
19.8 mm (0.8 in)
1955
27.2 mm (1.1 in)
1956
35.6 mm (1.4 in)
1957
24.9 mm (1.0 in)
1958
5.8 mm (0.23 in)
Wettest five days (Rx5day)
The wettest five days of the year at East Helena, 1925 to 1958. The record is 81.5 mm (3.2 in) in 1947, marked on the chart; the median year is 38.1 mm (1.5 in).
Wettest five days (Rx5day) at East Helena by year
Year
Wettest five days (Rx5day)
1925
n/a
1926
n/a
1927
61.8 mm (2.4 in)
1928
30.7 mm (1.2 in)
1929
32.1 mm (1.3 in)
1930
37.6 mm (1.5 in)
1931
25.1 mm (1.0 in)
1932
39.9 mm (1.6 in)
1933
70.7 mm (2.8 in)
1934
38.2 mm (1.5 in)
1935
24.4 mm (1.0 in)
1936
30.0 mm (1.2 in)
1937
46.3 mm (1.8 in)
1938
45.5 mm (1.8 in)
1939
32.2 mm (1.3 in)
1940
24.2 mm (1.0 in)
1941
42.3 mm (1.7 in)
1942
26.4 mm (1.0 in)
1943
59.7 mm (2.4 in)
1944
39.1 mm (1.5 in)
1945
37.9 mm (1.5 in)
1946
29.9 mm (1.2 in)
1947
81.5 mm (3.2 in)
1948
62.0 mm (2.4 in)
1949
36.3 mm (1.4 in)
1950
28.9 mm (1.1 in)
1951
43.2 mm (1.7 in)
1952
25.5 mm (1.0 in)
1953
52.5 mm (2.1 in)
1954
42.4 mm (1.7 in)
1955
36.4 mm (1.4 in)
1956
40.9 mm (1.6 in)
1957
46.1 mm (1.8 in)
1958
11.7 mm (0.5 in)
Longest dry spell (CDD)
The longest dry spell of the year at East Helena, 1925 to 1958. The record is 60 days in 1932, marked on the chart; the median year is 36 days.
Longest dry spell (CDD) at East Helena by year
Year
Longest dry spell (CDD)
1925
n/a
1926
n/a
1927
21 days
1928
45 days
1929
29 days
1930
39 days
1931
35 days
1932
60 days
1933
36 days
1934
44 days
1935
39 days
1936
31 days
1937
54 days
1938
32 days
1939
57 days
1940
32 days
1941
53 days
1942
35 days
1943
32 days
1944
35 days
1945
39 days
1946
37 days
1947
36 days
1948
37 days
1949
35 days
1950
36 days
1951
26 days
1952
29 days
1953
32 days
1954
45 days
1955
47 days
1956
34 days
1957
31 days
1958
36 days
Each chart shows one value per year; the dot marks the record year. TXx is the hottest daily maximum, TNn the coldest daily minimum, Rx1day and Rx5day the largest one-day and five-day rain totals, and CDD the longest run of days with less than 1 mm of rain. A year with missing days can understate an extreme.
Frost Dates and Growing Season
32 years with a frost
Across 32 years with a frost, the median last spring frost at East Helena falls on 18 May and the median first autumn frost on 21 September, which leaves a median of 130 days between them.
Fitted over all years, the growing season changes by -2.9 days per decade at this station.
Frost dates and growing season at East Helena
Measure
Median, all years
Earliest period
Recent period (1927 to 1957)
Recent against earliest
Fitted trend
Last spring frost
18 May
n/a
19 May
n/a
+2.4 days per decade
First autumn frost
21 September
n/a
21 September
n/a
-0.5 days per decade
Growing days
130 days
n/a
130 days
n/a
-2.9 days per decade
A frost day is a day with a daily minimum at or below 0 C (32 F). The last spring frost and the first autumn frost are the last and first such days of the cold season, and growing days are the days between them. A negative trend for the last spring frost means it comes earlier.
Download the Data
Data for East Helena standing records by year: CSV or JSON. Field meanings are on the data page.
Data for East Helena threshold days by year: CSV or JSON. Field meanings are on the data page.
Source: NOAA National Centers for Environmental Information, Global Historical Climatology Network Daily (GHCN-Daily). Records are computed by World Extreme Weather Monitor and are not official NOAA products. (US Government open data (NOAA NCEI)) Data as of 2026-10-15 (15 October 2026). Records are computed by this site and are not official.