Jefferson County International Airport

0S9 · Washington, United States

Climate Jefferson County International Airport 2020-2024

Climate and trends: average temperature, flight conditions, precipitation, wind speed and direction.

Calculated from historical METAR data of Jefferson County International Airport (K0S9) between 2020 and 2024.

VFR conditions (%)

Month Average 2024 2023 2022 2021 2020
January 59.9 80 61 39 51 56
February 66.5 91 75 57 65 68
March 70.1 67 77 56 81 67
April 70.7 64 79 79 75
May 68.8 71 63 71 74
June 69.6 65 65 82 69
July 72.9 76 71 68 69
August 75.1 85 76 76 82
September 74.6 80 87 82 54
October 69.4 65 78 64 63
November 63.1 68 67 56 65
December 51.7 49 43 44 57
Average 69.3 78.3 69.8 66.5 69.2 67.4

VFR conditions during daylight period

Percentage of observations where the VFR minimums for ceiling and visibility are met: visibility of 5 mi or more and a ceiling of 3,000 ft or more. Only observations between sunrise and sunset are taken into account.

Marginal VFR conditions (%)

Month Average 2024 2023 2022 2021 2020
January 85.5 91 92 75 85 90
February 87.8 96 93 86 85 89
March 92.8 94 94 89 97 91
April 94.3 94 94 95 98
May 90.6 92 93 92 96
June 91.6 86 92 95 94
July 91.5 94 91 81 91
August 89.4 96 86 93 97
September 89.0 93 95 92 69
October 87.2 82 89 92 84
November 87.1 91 89 81 92
December 82.6 76 90 85 84
Average 89.9 93.6 90.3 89.3 89.6 89.7

Marginal VFR conditions or better during daylight period

Percentage of observations where the MVFR minimums for ceiling and visibility are met: visibility of 3⅛ mi or more and a ceiling of 1,000 ft or more. Only observations between sunrise and sunset are taken into account.

Maximum temperatures (°C)

Month Average 2024 2023 2022 2021 2020
January 8.1 8 8 8 9 9
February 7.6 10 7 9 7 9
March 10.8 11 11 11 11 10
April 13.4 12 12 15 14
May 17.7 20 14 17 18
June 20.1 21 19 23 19
July 22.9 24 23 23 22
August 23.7 24 25 23 23
September 20.3 20 22 19 21
October 14.8 15 18 14 15
November 10.0 10 8 11 10
December 7.5 10 5 5 9
Average 14.1 9.5 15.2 14.8 14.7 14.8

Average highest temperature per day

The maximum temperature is typically observed some hours after noon.

Minimum temperatures (°C)

Month Average 2024 2023 2022 2021 2020
January 1.4 1 2 2 3 3
February 0.5 3 0 1 1 1
March 1.5 3 1 3 2 1
April 4.0 4 3 4 4
May 7.5 9 7 7 8
June 9.7 9 10 12 10
July 10.7 10 12 11 11
August 11.3 12 12 12 11
September 9.4 10 10 9 10
October 5.0 6 6 6 7
November 2.8 3 0 5 3
December 1.5 4 0 0 2
Average 5.1 2.2 5.8 5.5 5.8 5.8

Average lowest temperature per day

The minimum temperature is typically observed just before sunrise.

Precipitation (%)

Month Average 2024 2023 2022 2021 2020
January 5.5 19 10 0 7 5
February 7.7 13 16 2 4 4
March 5.4 13 12 3 3 3
April 5.3 17 5 2 4
May 3.2 5 4 1 4
June 3.5 7 3 3 4
July 0.4 2 0 0 1
August 0.9 3 1 0 1
September 2.8 7 1 4 2
October 4.9 11 10 5 1
November 6.1 5 12 9 5
December 6.2 9 12 10 3
Average 5.3 15.0 8.5 3.8 3.4 2.9

Precipitation during daylight period

Percentage of observations with observed rain, drizzle, snow or hail. Only observations between sunrise and sunset are taken into account.

Wind speed (knots)

Month Average 2024 2023 2022 2021 2020
January 4.9 5 5 4 5 6
February 4.6 5 4 4 5 4
March 5.2 6 6 5 6 5
April 5.7 6 7 5 5
May 4.6 4 5 5 5
June 4.6 5 5 5 4
July 4.0 4 4 4 4
August 4.3 4 4 4 5
September 4.6 5 5 5 4
October 4.6 5 4 5 5
November 4.7 4 4 6 5
December 3.9 4 4 4 4
Average 4.7 5.4 4.7 4.6 4.9 4.6

Average wind speed

Excluding wind gusts. Only observations between sunrise and sunset are taken into account.

Prevailing wind direction

Month 2024 2023 2022 2021 2020
January 140° 129° 161° 140° 142°
February 147° 148° 133° 137° 154°
March 145° 141° 192° 147° 282°
April 138° 141° 295° 321°
May 311° 332° 305° 234°
June 321° 292° 280° 293°
July 309° 301° 305° 298°
August 317° 310° 333° 289°
September 345° 314° 205° 250°
October 146° 212° 151° 241°
November 134° 260° 145° 171°
December 133° 148° 196° 137°

Prevailing wind direction

Average wind direction, weighed by wind speed. Only observations between sunrise and sunset are taken into account.