Photo: Esprqii · CC BY-SA 3.0Lake Oswego has cooler summers than 87% of U.S. towns
Deep winter brings January lows near 36°. From frosty January to warm July, readings climb 46°. Winters are mild: January nights here are milder than in 83% of U.S. towns. The frost-free window for a garden runs roughly March 18 to November 18.
A year in Lake Oswego at a glance
Each month’s typical high and low, and what it brings.
What stands out about Lake Oswego’s climate
Compared with towns across the U.S., with Lake Oswego’s place in Oregon beside it.
What a year in Lake Oswego feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 244 frost-free days a year
In half of years the last 32° night comes by March 18 and the first by November 18. Frost and day counts come from NOAA’s station at Oregon City, OR, 6 miles from the town’s center, at about the same height.
The 2023 USDA map puts Lake Oswego’s center in zone 9a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 20°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 4 inches of snow a winter
Snow, measured at Portland Kgw-tv, OR, is heaviest from January through February, about 1 inches a month. Precipitation (rain plus melted snow) adds up to 43 inches a year; December is the wettest month and July the driest. Rain or snow falls on about 155 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Lake Oswego
88% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Oregon City, OR.
Living with Lake Oswego’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
244 frost-free days in zone 9a. The last frost comes by Mar 18 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Nov 18.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August, September and October. 19 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Lake Oswego from natural hazards, earthquakes are the largest share (49%); heat waves, cold waves, winter storms and ice storms together are 11%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Lake Oswego and its neighbors
Every town next door is within a degree of Lake Oswego in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Lake Oswego’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Lake Oswego, OR | 36° | 81° | 43" | 3.6" |
| Ben Lomond, CA | 40° | 79° | 43" | 0.0" |
| Mercer Island, WA | 37° | 77° | 37" | 3.8" |
| Brigantine, NJ | 28° | 83° | 45" | 10" |
| Swannanoa, NC | 27° | 83° | 48" | 2.1" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Lake Oswego averaged 1.2° warmer than the 1900s. The biggest change is in January (+2.8°).
A smaller shift than in 59% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods.
How Lake Oswego compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Lake Oswego’s place among Oregon’s.
Lake Oswego weather by month
Highs, lows and precipitation from NOAA’s grid at Lake Oswego’s center; snow, wet days and snow on the ground from Portland Kgw-tv, OR. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 47° | 36° | 6.0" | 1.3" | 20 | 1 | 34° – 46° |
| February | 51° | 37° | 4.5" | 1.4" | 16 | 1 | 37° – 49° |
| March | 56° | 39° | 4.6" | 0.0" | 18 | 0 | 44° – 52° |
| April | 61° | 42° | 3.5" | 0.0" | 17 | 0 | 47° – 56° |
| May | 68° | 47° | 2.5" | 0.0" | 12 | 0 | 52° – 62° |
| June | 73° | 51° | 1.6" | 0.0" | 9 | 0 | 58° – 69° |
| July | 81° | 56° | 0.4" | 0.0" | 3 | 0 | 62° – 72° |
| August | 81° | 56° | 0.6" | 0.0" | 3 | 0 | 65° – 72° |
| September | 76° | 51° | 1.6" | 0.0" | 7 | 0 | 60° – 66° |
| October | 63° | 45° | 4.0" | 0.0" | 13 | 0 | 50° – 59° |
| November | 53° | 40° | 6.4" | 0.0" | 19 | 0 | 40° – 51° |
| December | 46° | 36° | 7.1" | 0.9" | 20 | 0 | 36° – 44° |
| Year | 63° | 45° | 42.8" | 3.6" | 155 | 2 |
How much a month can swing
A normal is an average. February swings the most: from 1991 to 2020 its average ranged from 37° to 49°. September is the most reliable, staying within 6°.
Where Lake Oswego’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Lake Oswego’s center.
- Snow: Portland Kgw-tv, OR.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Oregon City, OR, 6 miles from the town’s center, at about the same height; the nearest station that passes our checks for distance, height and agreement with the grid.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Lake Oswego’s climate
What is the weather like in Lake Oswego?
A typical July afternoon reaches 81°, a January night drops to 36°, and about 4 inches of snow falls in a normal winter. Milder January nights than 83% of U.S. towns; cooler July afternoons than 87% of U.S. towns.
How cold does it get in Lake Oswego in winter?
December nights average 36°. About 30 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 36°.
How much snow does Lake Oswego get?
About 3.6 inches in a normal winter at Portland Kgw-tv, OR, heaviest from January through February, about 1 inches a month, with snow on the ground about 2 days a year.
How hot does it get in Lake Oswego?
July, with a typical high of 81° and a low of 56°. About 20 days a year reach 90° and 2 reach 100° (Oregon City, OR).
When is the first and last frost in Lake Oswego?
In half of years the last spring frost (32°) comes by March 18 and the first fall frost by November 18, about 244 frost-free days, at Oregon City, OR.
What growing zone is Lake Oswego in?
Zone 9a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 20°.
What is the best time of year to visit Lake Oswego?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Lake Oswego getting warmer?
Yes: 1991–2020 averaged 1.2° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 59% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Lake Oswego.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.