Climate edit
_-_Eureka_Area,_CA(ThreadEx).svg)
Eureka has a mild, temperate cool-summer mediterranean climate (Köppen climate classification: Csb). Due to the influence of the Pacific Ocean and being on the shoreline of the cold-water Humboldt Bay, its temperatures are cooler than those of a typical mediterranean climate. Winters are mild and rainy, and summers are mild, cool, and dry. The average high in December, the coolest month, is 55.0 °F (12.8 °C), while the average high temperature in August, the warmest month, is 64.3 °F (17.9 °C), which is very mild and cool, respectively, for an area at such a southerly latitude. Eureka's average summer temperatures are much cooler than New York City and Istanbul which lie on the same latitude (and its average winter temperatures are also milder than those two cities); and are similar to those of Southeast Alaska, Scotland or Tierra del Fuego in southern Argentina and Chile, which lie well above the 50th parallel.
The seasonal temperature variation is very small; the difference between the August average of 58.5 °F (14.7 °C) and the December average of 47.8 °F (8.8 °C) is only 10.7 °F (5.9 °C), about equal to the diurnal temperature variation. Eureka is unique among mid-latitude climates in the northern hemisphere in that in more than 135 years of recorded temperatures, February has measured a warmer absolute maximum temperature than both the two high summer months of July and August. The absolute maximum temperature of July is merely 77 °F (25 °C) in spite of the high sun strength. The two warmest nights measured in Eureka were both during winter, as 18 January 1981 recorded a low of 63 °F (17 °C), tying a 26 February 1980 record.[1][2]
In addition, Eureka has a very short and milder range of temperatures compared to most of the contiguous US, with the all-time highest and lowest temperatures recorded in Eureka being only 87 °F (30.6 °C) on October 26, 1993, September 2, 2017,[3] and September 28, 2020,[4] and 20 °F (−6.7 °C) on January 14, 1888, respectively. On average, the highest temperature seen throughout the entire year is only 79 °F (26.1 °C), one of the coolest in the contiguous US, while on average the lowest temperature seen in the year (most often occurring at night) is only a similarly moderate 29 °F (−1.7 °C), yielding a very short and mild temperature range of about 50 °F (28 °C) throughout the year. Additionally, Eureka remains the only city on the West Coast of the continental United States to have never recorded a temperature of 90 °F (32.2 °C).
Temperatures drop to freezing or below only on a few nights per year, and daytime temperatures for these days are typically mild temperatures ranging between 43–58 °F (6.1–14.4 °C). Eureka has never recorded an ice day, with the coldest daytime maximum being 34 °F (1 °C) in 1990.[2] Between 1991 and 2020, the coldest daytime high of the year was 45 °F (7 °C) and the warmest night averaged 59 °F (15 °C).[2] NOAA’s weather station averages indicate only 0.18 in (4.6 mm) of rainfall in July, which is well within the mediterranean range, only with rainier winters, cooler and milder air than a typical mediterranean climate. Winter temperatures instead are similar to many climates found in Southern Europe from which basin the climate type is named.
The area experiences coastal fog throughout the year, especially during summer on the coast when temperatures in the city remain consistently around a mild 64 °F (17.8 °C). This phenomenon, together with cool breezes from the Pacific Ocean, keeps Eureka relatively cool and mild, while contrasting with inland areas in relative proximity to Humboldt Bay, which are prone to extreme temperatures that often exceed 100 °F (37.8 °C). This causes frequent temperature differences between Eureka and nearby inland areas during summer and early fall of 30 to 40 °F (17 to 22 °C). Despite the common coastal fog, Eureka enjoys on average about 55% possible sunshine per year, about on par with cities such as Calgary, Portland, New York City and Chicago.[5][6][7][8]
Annual precipitation averages 40.3 in (1,024 mm). Measurable precipitation falls on an average of 127.5 days each year, concentrated heavily from October to April. On average, December is the wettest month, averaging over 8 in (203.2 mm) of precipitation, virtually all of it rain. The wettest "rain year" was from July 1889 to June 1890 with 73.30 in (1,861.8 mm) and the driest from July 1976 to June 1977 with 17.56 in (446.0 mm). The greatest monthly precipitation was 23.21 in (589.5 mm) in December 2002. The greatest 24-hour precipitation was 6.79 in (172.5 mm) on December 27, 2002. However, historic 100-year dramatic weather events such as the Christmas Week flood of 1955 and, especially, the Christmas flood of 1964, which severely damaged the region, may not be reflected in records listed herein. Snowfall on the coast happens only on rare occasions, averaging 0.2 in (0.51 cm) as of the 1981–2010 normals, but only five years during that period received measurable snowfall.[9] The most snowfall in one month was 6.9 in (18 cm) in January 1907.
| Climate data for St Andrew’s (1991–2020 normals,[a] extremes 1886–present) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Year |
| Record high °F (°C) | 55 (13) |
57 (14) |
63 (17) |
68 (20) |
73 (23) |
79 (26) |
86 (30) |
82 (28) |
77 (25) |
68 (20) |
61 (16) |
55 (13) |
86 (30) |
| Mean maximum °F (°C) | 48 (9) |
50 (10) |
54 (12) |
61 (16) |
66 (19) |
72 (22) |
77 (25) |
75 (24) |
68 (20) |
61 (16) |
54 (12) |
50 (10) |
77 (25) |
| Mean daily maximum °F (°C) | 34 (1) |
36 (2) |
43 (6) |
50 (10) |
57 (14) |
63 (17) |
66 (19) |
64 (18) |
59 (15) |
54 (12) |
45 (7) |
37 (3) |
50.5 (10.3) |
| Daily mean °F (°C) | 30 (−1) |
32 (0) |
38.3 (3.5) |
45 (7) |
50.9 (10.5) |
56.3 (13.5) |
59.9 (15.5) |
59 (15) |
54 (12) |
48 (9) |
40.1 (4.5) |
34 (1) |
45.59 (7.55) |
| Mean daily minimum °F (°C) | 27 (−3) |
28 (−2) |
34 (1) |
39 (4) |
45 (7) |
50 (10) |
54 (12) |
54 (12) |
48 (9) |
43 (6) |
36 (2) |
30 (−1) |
40.6 (4.8) |
| Mean minimum °F (°C) | 16 (−9) |
18 (−8) |
21 (−6) |
28 (−2) |
36 (2) |
43 (6) |
46 (8) |
46 (8) |
39 (4) |
34 (1) |
27 (−3) |
19 (−7) |
16 (−9) |
| Record low °F (°C) | 0 (−18) |
3 (−16) |
10 (−12) |
18 (−8) |
27 (−3) |
32 (0) |
39 (4) |
39 (4) |
34 (1) |
27 (−3) |
21 (−6) |
7 (−14) |
0 (−18) |
| Average precipitation inches (mm) | 1.2 (30) |
0.8 (20) |
1.6 (40) |
2.0 (50) |
1.6 (40) |
2.0 (50) |
2.4 (60) |
2.4 (60) |
2.0 (50) |
2.8 (70) |
3.1 (80) |
1.6 (40) |
23.2 (590) |
| Average snowfall inches (cm) | 12 (30) |
9 (23) |
6 (15) |
3 (7.6) |
0.1 (0.25) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
0.0 (0.0) |
2 (5.1) |
4 (10) |
36.1 (92) |
| Average precipitation days (≥ 0.01 in) | 15 | 11 | 10 | 8 | 5 | 5 | 6 | 6 | 5 | 7 | 10 | 8 | 96 |
| Average snowy days (≥ 0.1 in) | 12 | 9 | 6 | 3 | 0.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 2.0 | 4.0 | 36.1 |
| Mean monthly sunshine hours | 90 | 110 | 130 | 160 | 180 | 200 | 180 | 160 | 150 | 120 | 100 | 80 | 1,660 |
| Source: NOAA (sun 1961–1990)[9][10][11] | |||||||||||||
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See or edit raw graph data.
- ^ "NWS Eureka - Climate Record Extremes". National Weather Service. Retrieved 3 June 2022.
- ^ a b c "Climate data for Eureka". National Weather Service. Retrieved 3 June 2022.
- ^ "Archived copy". Archived from the original on September 17, 2017. Retrieved September 3, 2017.
{{cite web}}: CS1 maint: archived copy as title (link) - ^ "Climate".
- ^ "Table" (PDF). ftp.atdd.noaa.gov. Retrieved 2019-09-26.
- ^ "Table" (PDF). ftp.atdd.noaa.gov. Retrieved 2019-09-26.
- ^ "Table" (PDF). ftp.atdd.noaa.gov. Retrieved 2019-09-26.
- ^ "Canadian Climate Normals 1981–2010 Station Data – Climate – Environment and Climate Change Canada". 2013-09-25.
- ^ a b "NowData – NOAA Online Weather Data". National Oceanic and Atmospheric Administration. Retrieved September 23, 2013.
- ^ "U.S. Climate Normals Quick Access – Station: Eureka WFO Woodley Island, CA". National Oceanic and Atmospheric Administration. Archived from the original on 2023-05-08. Retrieved February 23, 2023.
- ^ "WMO Climate Normals for Eureka/WSO City, CA 1961–1990". National Oceanic and Atmospheric Administration. Archived from the original on 2023-05-08. Retrieved September 23, 2015.
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