Photo: UncleVinny · CC BY 3.0Penryn’s winters are milder than most of the U.S.; July afternoons average 95°
A typical July afternoon reaches 95°, a January night drops to 38°.
A year in Penryn at a glance
Each month’s typical high and low, and what it brings.
What stands out about Penryn’s climate
Compared with towns across the U.S., with Penryn’s place in California beside it.
What a year in Penryn feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 286 frost-free days a year
In half of years the last 32° night comes by February 25 and the first by December 5. Frost and day counts come from Auburn, CA, 6 miles away.
The 2023 USDA map puts Penryn’s center in zone 9b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 26°. 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 27 inches of rain a year
January is the wettest month and July the driest.
Rain + melted snow by month
Inches of water
Heating and cooling a home in Penryn
66% of the work is heating. Months averaging under 55° run from November through March.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Auburn, CA.
Living with Penryn’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
286 frost-free days in zone 9b. The last frost comes by Feb 25 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Dec 5.
Months with highs of 62–84° and lows of 40° or more: March, April, May, October and November. 0.0 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Penryn from natural hazards, river flooding is the largest share (47%); heat waves, cold waves, winter storms and ice storms together are 1%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Penryn and similar climates
TownRatings has no climate map of the towns around Penryn yet.
Temperatures and precipitation come from NOAA’s 5 km grid; snow and day counts from the stations named on this page.
Warmer than it used to be
The last 30 years in Penryn averaged 1.0° warmer than the 1900s. The biggest change is in September (+1.8°).
A smaller shift than in 77% 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 Penryn compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Penryn’s place among California’s.
Penryn weather by month
Highs, lows and precipitation from NOAA’s grid at Penryn’s center. 1991–2020 normals.
| Month | High | Low | Rain + melt | 30-yr range |
|---|---|---|---|---|
| January | 56° | 38° | 5.3" | 44° – 52° |
| February | 61° | 41° | 4.8" | 46° – 55° |
| March | 65° | 43° | 3.9" | 48° – 60° |
| April | 71° | 46° | 2.2" | 53° – 62° |
| May | 80° | 52° | 1.2" | 58° – 73° |
| June | 89° | 57° | 0.3" | 67° – 78° |
| July | 95° | 62° | 0.0" | 74° – 82° |
| August | 94° | 61° | 0.0" | 74° – 82° |
| September | 89° | 58° | 0.2" | 70° – 77° |
| October | 78° | 50° | 1.2" | 61° – 69° |
| November | 65° | 43° | 2.8" | 46° – 59° |
| December | 56° | 38° | 4.7" | 43° – 51° |
| Year | 75° | 49° | 26.6" |
How much a month can swing
A normal is an average. May swings the most: from 1991 to 2020 its average ranged from 58° to 73°. September is the most reliable, staying within 7°.
Where Penryn’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 Penryn’s center.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Auburn, CA, 6 miles from the town’s center, 730 ft higher; no station nearby passes every check; this is the nearest one in the same valley, flagged above.
- 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 Penryn’s climate
What is the weather like in Penryn?
A typical July afternoon reaches 95°, a January night drops to 38°. Milder January nights than 85% of U.S. towns; hotter July afternoons than 95% of U.S. towns.
How cold does it get in Penryn in winter?
December nights average 38°. About 20 nights a year reach 32° or below. In the coldest December of the last 30 years the month averaged 43°.
How hot does it get in Penryn?
July, with a typical high of 95° and a low of 62°. About 63 days a year reach 90° and 7 reach 100° (Auburn, CA).
When is the first and last frost in Penryn?
In half of years the last spring frost (32°) comes by February 25 and the first fall frost by December 5, about 286 frost-free days, at Auburn, CA.
What growing zone is Penryn in?
Zone 9b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 26°.
What is the best time of year to visit Penryn?
By one simple rule (highs of 62–84° and lows of 40° or more), March, April, May, October and November. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Penryn getting warmer?
Yes: 1991–2020 averaged 1.0° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 77% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Penryn.
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.