Climate and monthly weather forecastIssaquah, WA
Climate and monthly weather forecast
The climate of Issaquah
Issaquah, a city in Washington, USA, mirrors a Mediterranean, warm summer climate, predominantly known as Csb according to the Köppen climate classification. Appreciating its geographical location, it's nestled next to the Sammamish Plateau, to the east of Seattle. It's enveloped in fertile valleys and flanked by colossal mountains. This geography has a significant influence on its climate.Throughout the year, Issaquah experiences fluctuations in weather conditions, bearing witness to varying climate patterns. Balancing between a high of 77°F (25°C) in the warmest month and a low of 33.4°F (0.8°C) in the coldest, temperatures show substantial shifts across seasons. The monthly average humidity percolates from 69% to 85%, indicating higher levels of moisture during colder months.
Rainfall, another crucial climatic variable, predominantly hits a mark from approximately 0.24" (6mm) to 2.01" (51mm) monthly. An intriguing pattern emerges where the heaviest rainfall days co-align with the coldest months. A similar pattern is observed in sunshine hours, with the lowest span of 4 hours during colder months, gradually escalating to a peak of 10.5 hours in sunnier times. Also, snowfall remains inconsiderable, with minimal observations from 0" (0mm) to 0.94" (24mm).
The best time to visit Issaquah
Determining the ideal time to visit Issaquah bears relevance to individual preferences. Nonetheless, the period from June to September can be deemed as a good time for tourists. During this period, daylight hours extend from 15.1 hours to 15.5 hours, providing ample time to explore the expanse of the city. This period also sees less rainfall, with numbers dwindling from 0.55" (14mm) to 0.24" (6mm), retaining the outdoor charm for sightseers.The worst time to visit Issaquah
The period from November to January could pose as less favorable for visiting Issaquah. Predominantly, the lowest temperatures are observed during these months, with the mercury dropping to 33.4°F (0.8°C). Apart from plummeting temperatures, heavy rainfall can also be expected, ranging from 1.5" (38mm) to 2.01" (51mm). Reduced daylight hours between 8.5 hours to 9.3 hours may curtail outdoor activities.Spring weather in Issaquah
Spring in Issaquah witnesses an uplift in weather conditions, particularly during March to May. The temperatures move from 50°F (10°C) to 64.6°F (18.1°C). This period also observes reduced rainfall, from 1.22" (31mm) to 0.63" (16mm), and increased daylight hours from 11.9 hours to 15.1 hours, contributing to a pleasant atmosphere.Summer weather in Issaquah
From June to August, the city revels in its warmest months with average temperatures ranging from 69.4°F (20.8°C) to 77°F (25°C). Rainfall is at its minimum, ranging merely from 0.55" (14mm) to 0.24" (6mm), and the daylight stretches from 15.9 hours to 15.5 hours, favoring outdoor activities. This season also brings peak sunshine hours from 9 hours to 10.5 hours, graciously illuminating the city.Autumn weather in Issaquah
Autumn months from September to November mark a mild dip in temperatures, from 70°F (21.1°C) to 48.4°F (9.1°C), and a surge in rainfall from 0.63" (16mm) to 1.5" (38mm). The daylight hours range from 12.5 hours to 9.3 hours, with a proportionate decline in sunshine hours.Winter weather in Issaquah
The winter, spanning December to February, ushers in the coldest months with temperatures oscillating from 42.3°F (5.7°C) to 44.2°F (6.8°C). A significant increase in humidity and cloud cover, especially during the end and beginning of the year, indicate a more glacial environment. Rainfall fluctuates between 1.3" (33mm) and 2.01" (51mm), while daylight hours reach their minimum, from 8.5 hours to 9 hours, alongside reduced sunshine hours.Weather in January
The weather in January in Issaquah, Washington is consistent with the beginning of the year. This month faces the highest levels of relative humidity, at 85%, and reduced daylight hours of 9. Erratic weather conditions prevail, combining cold temperatures, rainfall, and snowfall. Weather in January »Weather in February
The shift to February brings slight relief from the January cold. It also retains the relatively high humidity but witnesses an increase in daylight hours from 9 to 10.3. Snowfall is relatively common with 2.5 days recorded. However, rainfall does decrease as February has lesser rainfall inches, 1.3 compared to 1.85 in January. Weather in February »Weather in March
Moving into March, Issaquah begins to experience transitional weather. Compared to February, you will notice an improvement in visibility, increasing from 4 mi to 5 mi. The city indulges in longer daylight hours, now reaching nearly 12, and fewer days with snowfall, going down to 0.8. Weather in March »Weather in April
Arriving in April, Issaquah blossoms into the splendor of spring. Sunlight conditions drastically ameliorate, allotting the residents an amplified 7.6 hours of sunshine on average. The increased daylight hours, 13.7 in total, promise longer days. Weather in April »Weather in May
In May, the residents of Issaquah experience clear skies as the city prepares to welcome summer. Severe winter weather is a distant memory, and there's a lull in the prevalence of rain—in fact, May sees the highest level of sunshine hours in the year at 8.8. Weather in May »Weather in June
June, the door to summer, brings minimal changes in weather patterns from May. There's a noticeable drop in rainfall with only 0.55" (14mm), presenting the perfect opportunity for outdoor activities. Hours of daylight exceed the past months, reaching its peak at 15.9 hours, encouraging residents to make the most of the fair weather conditions. Weather in June »Weather in July
The heart of summer, July, sees Issaquah basking in warm weather. July celebrates the highest average temperature of the year at 76.1°F (24.5°C), encouraging a stream of sun enthusiasts. With minimum recorded rainfall, 0.24" (6mm), and the peak of UV index at 5, it's definitely a month for sunblock. Weather in July »Weather in August
August carries forward the warm temperatures from July with a further increase to 77°F (25°C) on average. The rainfall also shows an infinitesimal rise to 0.28" (7mm). Meanwhile, the evenings stay warmer as August records the highest average low temperature in the year at 51.4°F (10.8°C). Weather in August »Weather in September
September indicates an impending shift towards cooler temperatures. Despite this hint, it stays fairly warm with the UV index holding steady at 4. Cloud cover increases from 27% in August to 36% in September. Rainfall reemerges as a significant weather element with 0.63" (16mm) recorded—an increase from August's mere 0.28" (7mm). Weather in September »Weather in October
October symbolizes the onset of Autumn and brings about a notable change in weather conditions. Average high temperature drops from 70°F (21.1°C) in September to 58.6°F (14.8°C), indicating the much-awaited retreat from summer. Weather in October »Weather in November
November ushers in an even cooler phase in Issaquah, as winter begins to make its presence felt. A significant drop in the average high temperature to 48.4°F (9.1°C) — a steep fall from October — lends a characteristic chill to the air. Weather in November »Weather in December
December endorses the onset of winter with an average low temperature of 33.4°F (0.8°C), the lowest in the year. Straddling the threshold of freeze, the days are short with only 8.5 hours of daylight—the least in the year. Weather in December »Updated: Aug 20, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
January and February, with an average relative humidity of 85%, are most humid months.
Throughout the year, there are 127.4 rainfall days, and 12.52" (318mm) of precipitation is accumulated.
January through April, November and December are months with snowfall.
In Issaquah, during the entire year, snow falls for 5.9 days and aggregates up to 1.93" (49mm) of snow.
The months with the lowest UV index are January, February, November and December, with an average maximum UV index of 2.
The month with the most snowfall is February, when snow falls for 2.5 days and typically aggregates up to 0.94" (24mm) of snow.
On Sunday, March 10. 2024, at 2:00 am, Daylight Saving Time starts, and the time zone changes from PST to PDT. Daylight Saving Time ends Sunday, November 3. 2024, at 2:00 am, and the time zone reverts from PDT to PST.
May through October are months without snowfall.
The month with the longest days in Issaquah, Washington, is June, with an average of 15h and 54min of daylight.
With an average relative humidity of 69%, July is the least humid month.
July is the month with the least rainfall. Rain falls for 4.9 days and accumulates 0.24" (6mm) of precipitation.
July is the month with the highest UV index, with an average maximum UV index of 5.
In Issaquah, August is the month with the highest recorded average temperatures, measuring a high of 77°F (25°C) and a low of 51.4°F (10.8°C).
August has the most sunshine of the year, with an average of 10.5h of sunshine.
In Issaquah, the lowest temperatures are generally noted in December, averaging a high of 42.3°F (5.7°C) and a low of 33.4°F (0.8°C).
The month with the most rainfall is December, when the rain falls for 13.7 days and typically aggregates up to 2.01" (51mm) of precipitation.
December has the shortest days of the year, with an average of 8h and 30min of daylight.
The month with the least sunshine is December, with an average of 4h of sunshine.
Average temperature
Issaquah, WA
The warmest month (with the highest average high temperature) is August (77°F).
The month with the lowest average high temperature is December (42.3°F).
The month with the highest average low temperature is August (51.4°F).
The coldest months (with the lowest average low temperature) are February and December (33.4°F).
Average pressure
Issaquah, WA
- Average pressure in January:
30.1"Hg - Average pressure in February:
30.06"Hg - Average pressure in March:
30.01"Hg - Average pressure in April:
30.04"Hg - Average pressure in May:
30.02"Hg - Average pressure in June:
30.01"Hg
- Average pressure in July:
30.03"Hg - Average pressure in August:
30"Hg - Average pressure in September:
30.01"Hg - Average pressure in October:
30.04"Hg - Average pressure in November:
30.04"Hg - Average pressure in December:
30.09"Hg
The month with the highest atmospheric pressure is January (30.1"Hg).
The month with the lowest atmospheric pressure is August (30"Hg).
Average wind speed
Issaquah, WA
- Average wind speed in January:
5.1mph - Average wind speed in February:
4.7mph - Average wind speed in March:
4.8mph - Average wind speed in April:
4.2mph - Average wind speed in May:
3.8mph - Average wind speed in June:
3.7mph
- Average wind speed in July:
3.5mph - Average wind speed in August:
3.4mph - Average wind speed in September:
3.7mph - Average wind speed in October:
4.1mph - Average wind speed in November:
4.7mph - Average wind speed in December:
4.7mph
The windiest month (with the highest average wind speed) is January (5.1mph).
The calmest month (with the lowest average wind speed) is August (3.4mph).
Average humidity
Issaquah, WA
The months with the highest relative humidity are January and February (85%).
The month with the lowest relative humidity is July (69%).
Average rainfall
Issaquah, WA
- Average rainfall in January:
1.85" - Average rainfall in February:
1.3" - Average rainfall in March:
1.22" - Average rainfall in April:
1.02" - Average rainfall in May:
0.63" - Average rainfall in June:
0.55"
The wettest month (with the highest rainfall) is December (2.01").
The driest month (with the least rainfall) is July (0.24").
Average rainfall days
Issaquah, WA
- Average rainfall days in January:
13.5 days - Average rainfall days in February:
11.7 days - Average rainfall days in March:
14.8 days - Average rainfall days in April:
13.1 days - Average rainfall days in May:
9.6 days - Average rainfall days in June:
8.8 days
- Average rainfall days in July:
4.9 days - Average rainfall days in August:
4.3 days - Average rainfall days in September:
7.8 days - Average rainfall days in October:
11.8 days - Average rainfall days in November:
13.4 days - Average rainfall days in December:
13.7 days
The month with the highest number of rainy days is March (14.8 days).
The month with the least rainy days is August (4.3 days).
Average snowfall
Issaquah, WA
The month with the highest snowfall is February (0.94").
The months with the least snowfall are May, June, July, August, September and October (0").
Average snowfall days
Issaquah, WA
- Average snowfall days in January:
1.3 days - Average snowfall days in February:
2.5 days - Average snowfall days in March:
0.8 days - Average snowfall days in April:
0.2 days - Average snowfall days in May:
0 days - Average snowfall days in June:
0 days
- Average snowfall days in July:
0 days - Average snowfall days in August:
0 days - Average snowfall days in September:
0 days - Average snowfall days in October:
0 days - Average snowfall days in November:
0.3 days - Average snowfall days in December:
0.8 days
The month with the highest number of snowfall days is February (2.5 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average daylight / Average sunshine
Issaquah, WA
- Average daylight in January:
9h and 0min - Average daylight in February:
10h and 18min - Average daylight in March:
11h and 54min - Average daylight in April:
13h and 42min - Average daylight in May:
15h and 12min - Average daylight in June:
15h and 54min
- Average daylight in July:
15h and 30min - Average daylight in August:
14h and 12min - Average daylight in September:
12h and 30min - Average daylight in October:
10h and 48min - Average daylight in November:
9h and 18min - Average daylight in December:
8h and 30min
The month with the longest days is June (Average daylight: 15h and 54min).
The month with the shortest days is December (Average daylight: 8h and 30min).
- Average sunshine in January:
4h and 6min - Average sunshine in February:
4h and 12min - Average sunshine in March:
5h and 54min - Average sunshine in April:
7h and 36min - Average sunshine in May:
8h and 48min - Average sunshine in June:
9h and 0min
- Average sunshine in July:
10h and 18min - Average sunshine in August:
10h and 30min - Average sunshine in September:
9h and 6min - Average sunshine in October:
5h and 24min - Average sunshine in November:
4h and 24min - Average sunshine in December:
4h and 0min
The month with the most sunshine is August (Average sunshine: 10h and 30min).
The month with the least sunshine is December (Average sunshine: 4h and 0min).
Average sunshine days
Issaquah, WA
- Average sunshine days in January:
15.8 days - Average sunshine days in February:
12.9 days - Average sunshine days in March:
13.3 days - Average sunshine days in April:
14.3 days - Average sunshine days in May:
18.4 days - Average sunshine days in June:
18.7 days
- Average sunshine days in July:
24.9 days - Average sunshine days in August:
25 days - Average sunshine days in September:
19 days - Average sunshine days in October:
17.4 days - Average sunshine days in November:
14.5 days - Average sunshine days in December:
14.8 days
The month with the most sunshine days is August (25 days).
The month with the least sunshine days is February (12.9 days).
Average UV index
Issaquah, WA
The month with the highest UV index is July (UV index 5).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover
Issaquah, WA
The months with the most cloud cover are January and December (Cloud cover 58).
The month with the least cloud cover is August (Cloud cover 27).
Average visibility
Issaquah, WA
The months with the highest visibility are July and August (6mi).
The months with the lowest visibility are January, February and December (4mi).
