Climate and monthly weather forecast
Lewiston, ID

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A scenic and dramatic landscape on both sides of the glorious Lewiston City in Idaho, and a clear view of the iconic Snake river passing through
A scenic and dramatic landscape on both sides of the glorious Lewiston City in Idaho, and a clear view of the iconic Snake river passing through

The climate of Lewiston

Lewiston, Idaho, positioned within the climatic zone defined by the Köppen classification as Mediterranean warm summer (Csb), experiences rather mild and comfortable weather throughout the year. The yearly averages indicate a significant fluctuation in temperature, mirroring the changing seasons. Here, the mercury soars to an annual high of 85.3°F (29.6°C) in the peak summer months while plummeting to a chilly low of 24.4°F (-4.2°C) in the frigid winter months.

Humidity spans from 38% in August to a saturated 84% in January, indicating a clear contrast between the arid summer and humid autumn and winter. Rainfall displays a similar disparity, with January seeing the heaviest showers at 1.77" (45mm) compared to a somewhat arid 0.31" (8mm) in August. Snowfall, on the other hand, registers its peak in January and February with 2.56" (65mm) while staying absent from May through October.

Lewiston's sunny charm is most evident amid the long summer daylight hours, reaching a stretch of 15.8 hours in June, though sunshine hours peak at 12 in July and August. The UV index likewise peaks at 7 in July, necessitating protective measures during outdoor activities. Interestingly, despite seasonal fluctuations in other weather parameters, atmospheric pressure and visibility show little month-to-month variation.

The best time to visit Lewiston

Weather-wise, the best period to travel to Lewiston depends largely on the preferred activities of visitors. However, considering the climatic averages, the summer months, from June to August can be considered ideal. During this period, the mean temperatures hover around 71.8°F (22.1°C) to 85.3°F (29.6°C), perfect for exploring the outdoor beauty of Lewiston. Rainfall is also at its lowest, averaging between 0.31" (8mm) to 0.39" (10mm), and accompanied by 15.4 to 15.8 hours of daylight which makes it absolutely splendid for various excursions.

The worst time to visit Lewiston

Winters, spanning December to February, may prove somewhat challenging for visits due to the frigid temperatures that drop down to between 24.4°F (-4.2°C) to 37.4°F (3°C). This is complemented by substantial snowfall of 0.55" (14mm) to 3.27" (83mm). The shorter daylight hours, between 8.7 to 10.4, coupled with reduced visibility, might deter visitors who prefer outdoor activities, making this period less desirable for travel.

Spring weather in Lewiston

Spring in Lewiston is seen from March to May with temperatures rising smoothly from 48.6°F (9.2°C) at the start to 65.1°F (18.4°C) towards the end of the season. Humidity and rainfall decrease gradually during this period, signaling the transition towards a dryer season. Sunshine hours extend from 7.1 hours to 10.6 hours, making the days longer and ideal for outdoor activities. Despite the increasing temperatures, the UV index remains moderate, ranging from 3 to 4.

Summer weather in Lewiston

The summer months from June to August in Lewiston are typically warm and dry. Temperatures climb steadily to reach their pinnacle at 85.3°F (29.6°C) in August. Coupled with this, rainfall dwindles to its annual lowest between 0.31" (8mm) to 0.39" (10mm), indicating arid conditions. While the daylight hours recede slightly from 15.8 efforts in June to 14.1 hours in August, the sunshine hours peak to their maximum of 12 hours in July and August, painting the city in bright, sunlit hues.

Autumn weather in Lewiston

Autumn, observed from September to November, is characterized by a progressive drop in temperatures from 75°F (23.9°C) in September to 46°F (7.8°C) in November. Rainfall begins to increment from 0.39" (10mm) in September to 1.26" (32mm) by November, hinting towards the wetter winter season. The daylight hours also decrease significantly from 12.5 hours in September to 9.4 hours in November. However, despite the decreasing temperatures and shortening days, humidity levels remain quite comfortable, making autumn still an attractive season for tourists.

Winter weather in Lewiston

Winter sets in Lewiston from December to February, bringing with it lower temperatures, ranging from 24.4°F (-4.2°C) to 37.4°F (3°C). This period also sees the highest precipitation in the form of cold rainfall and snow, accumulating between 1.77" (45mm) to 1.85" (47mm) of rain and experiencing between 2.1 to 8.1 days of snowfall. Daylight is limited between 8.7 to 10.4 hours and the sunshine duration dwindles to between 5.1 to 6.4 hours. Winter in Lewiston, nevertheless, offers a whole different charm to its weather-loving visitors.

Weather in January

January brings the chill of winter to Lewiston, Idaho, as the coldest period settles in. The weather fluctuates from an average high of 37.4°F (3°C) to an average low of 27°F (-2.8°C). Snow is customary and tends to blanket the city, complementing the crisp chill with a pristine white landscape. Weather in January »

Weather in February

Moving into February, weather conditions remain cold albeit a slight increase is observed when compared to January. The city sees its most substantial snowfall of the year, accumulating 3.27" (83mm). The lengthening of daylight hours hints at the approaching spring season. Weather in February »

Weather in March

The transition of winter into spring commences in March. Compared to February, a noticeable increase in temperatures allows the accumulated snow to begin its thaw. Rainfall becomes more prevalent, transitioning from the quieter and delicate snowflakes of winter. Weather in March »

Weather in April

April marks the onset of a more noticeable spring weather, bringing substantial changes when compared to the colder March. Substantial sunshine hours, around 9.7 per day on average, highlight the transition towards more favorable weather conditions. Weather in April »

Weather in May

May experiences a considerable shift to welcomingly warm weather conditions in Lewiston. The rise in temperature does not bring excessive heat but rather the promise of a pleasant summer ahead. Longer daylight hours and a drop in humidity enhance the comfort level for residents. Weather in May »

Weather in June

June carries the torch of the warm season, exhibiting a considerable rise in temperature from May. Lewiston records the lowest relative humidity at an average of 65%, making the days pleasant and largely free from oppressive mugginess. Weather in June »

Weather in July

July showcases peak summer conditions, recording an average high temperature of 84°F (28.9°C). The extended daylight hours maximize outdoor activity time, while a slight increase in evening temperatures provides comfortable summer nights. Weather in July »

Weather in August

Weather in August remains characterized by high temperatures, nearly mirroring July’s conditions. A slight difference in sunrise and sunset times sees daylight hours decreasing, hinting towards the oncoming fall. Despite being one of the driest months, with a scanty rainfall of 0.31" (8mm), the environment remains adequately hydrated due to water bodies in the region. Weather in August »

Weather in September

Lewiston's September climate marks the beginning of mild autumnal conditions from the hot summer of August. Cooler temperatures begin to creep in, especially during the mornings, making the climate more bearable. The UV index starts to decline and the hours of sunshine decrease, aligning with the shortening of days. Weather in September »

Weather in October

October ushers in a noticeable shift from the mild climate of September to the chillier autumn weather. The fall colors peak all over Lewiston, contrasting with the cool blue skies. Rainfall steadily increases but remains sporadic, allowing residents to enjoy crisp sunny days amid the changing leaves. Weather in October »

Weather in November

In November, Lewiston witnesses the full onset of late fall, with a visible decrease in temperature from October. Temperatures dip and Lewiston experiences early winter snowfall of approx 0.55" (14mm). With the arrival of shorter days and longer nights, residents bundle up in warmer garments. Weather in November »

Weather in December

Winter takes full effect in December with temperatures dropping significantly from November. The snowfall equivalent to January resumes, blanketing Lewiston in a white cover once again. Daylight is at its minimal, with imminent Christmas festivities lighting up the long and chilly nights. Weather in December »
Updated: Feb 12, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What is the most humid month in Lewiston?

January is the most humid month, with an average relative humidity of 84%.

How much does it rain in Lewiston?

Throughout the year, in Lewiston, Idaho, there are 142.4 rainfall days, and 14.21" (361mm) of precipitation is accumulated.

When does it snow in Lewiston?

January through April, October through December are months with snowfall in Lewiston, Idaho.

How much does it snow in Lewiston?

Throughout the year, in Lewiston, there are 24.2 snowfall days, and 10.16" (258mm) of snow is accumulated.

What is the month with the least sunshine in Lewiston?

January has the least sunshine of the year, with an average of 5.1h of sunshine.

What is the snowiest month in Lewiston?

February is the month with the most snowfall. Snow falls for 6.5 days and accumulates 3.27" (83mm) of snow.

What is the month with the lowest UV index in Lewiston?

February is the month with the lowest UV index in Lewiston, with an average maximum UV index of 1.

What is the rainiest month in Lewiston?

The month with the most rainfall is March, when the rain falls for 17.6 days and typically aggregates up to 1.85" (47mm) of precipitation.

When is Daylight Saving Time (DST) in Lewiston?

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.

When it does not snow in Lewiston?

May through September are months without snowfall in Lewiston.

When are the longest days in Lewiston?

The month with the longest days is June, with an average of 15h and 42min of daylight.

What is the month with the highest UV index in Lewiston?

With an average maximum UV index of 7, July is the month with the highest UV index.

What time of the year is the hottest in Lewiston?

August is the warmest month in Lewiston, Idaho, exhibiting average temperatures of 85.3°F (29.6°C) at the peak and 59.2°F (15.1°C) at the base.

What is the least humid month in Lewiston?

The least humid month in Lewiston is August, with an average relative humidity of 38%.

What is the driest month in Lewiston?

August is the month with the least rainfall. Rain falls for 5.2 days and accumulates 0.31" (8mm) of precipitation.

What month has the most sunshine in Lewiston?

With an average of 12h of sunshine, August has the most sunshine of the year in Lewiston.

What is the coldest time of year in Lewiston?

The coldest period in Lewiston, Idaho, is December, when temperatures fluctuate between an average high of 36.1°F (2.3°C) and a low of 24.4°F (-4.2°C).

What is the month with the shortest days in Lewiston?

December has the shortest days of the year in Lewiston, Idaho, with an average of 8h and 42min of daylight.

Average temperature
Lewiston, ID

Average temperature - Lewiston, ID

The warmest month (with the highest average high temperature) is August (85.3°F).
The month with the lowest average high temperature is December (36.1°F).

The month with the highest average low temperature is August (59.2°F).
The coldest month (with the lowest average low temperature) is December (24.4°F).

Average pressure
Lewiston, ID

Average pressure - Lewiston, ID

The month with the highest atmospheric pressure is January (30.2"Hg).
The month with the lowest atmospheric pressure is August (29.91"Hg).

Average wind speed
Lewiston, ID

Average wind speed - Lewiston, ID

The windiest month (with the highest average wind speed) is April (5.7mph).
The calmest months (with the lowest average wind speed) are July, August and September (4.3mph).

Average humidity
Lewiston, ID

Average humidity - Lewiston, ID

The month with the highest relative humidity is January (84%).
The month with the lowest relative humidity is August (38%).

Average rainfall
Lewiston, ID

Average rainfall - Lewiston, ID

The wettest month (with the highest rainfall) is March (1.85").
The driest month (with the least rainfall) is August (0.31").

Average rainfall days
Lewiston, ID

Average rainfall days - Lewiston, ID

The month with the highest number of rainy days is March (17.6 days).
The month with the least rainy days is August (5.2 days).

Average snowfall
Lewiston, ID

Average snowfall - Lewiston, ID

The month with the highest snowfall is February (3.27").
The months with the least snowfall are May, June, July, August and September (0").

Average snowfall days
Lewiston, ID

Average snowfall days - Lewiston, ID

The month with the highest number of snowfall days is December (8.1 days).
The months with the least snowfall days are May, June, July, August and September (0 days).

Average daylight / Average sunshine
Lewiston, ID

Average daylight / Average sunshine - Lewiston, ID

The month with the longest days is June (Average daylight: 15h and 42min).
The month with the shortest days is December (Average daylight: 8h and 42min).

The month with the most sunshine is August (Average sunshine: 12h and 0min).
The month with the least sunshine is January (Average sunshine: 5h and 6min).

Average sunshine days
Lewiston, ID

Average sunshine days - Lewiston, ID

The month with the most sunshine days is July (24 days).
The months with the least sunshine days are February and March (10.8 days).

Average visibility
Lewiston, ID

Average visibility - Lewiston, ID

The months with the highest visibility are March, April, May, June, July, August, September, October and November (6mi).
The months with the lowest visibility are January, February and December (5mi).

Lewiston, Idaho, USA

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