Crystal Lake sits near the bottom of U.S. towns for winter warmth
July afternoons average 82°. A year here swings 74° from midwinter lows to midsummer highs. Summers stay cool: July afternoons here are cooler than in 83% of U.S. towns. Warm coats and heating bills mark the months from October to April, when means dip under 50°.
A year in Crystal Lake at a glance
Each month’s typical high and low, and what it brings.
What stands out about Crystal Lake’s climate
Compared with towns across the U.S., with Crystal Lake’s place in Iowa beside it.
What a year in Crystal Lake feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 159 frost-free days a year
In half of years the last 32° night comes by April 30 and the first by October 7. Frost and day counts come from NOAA’s station at Forest City 2 Nne, IA, 9 miles from the town’s center, at about the same height.
The 2023 USDA map puts Crystal Lake’s center in zone 5a: the coldest night of a typical winter, averaged over 1991–2020, reaches about −19°. 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 44 inches of snow a winter
Snow, measured at Mason City Muni Airport, falls mostly in January. Precipitation (rain plus melted snow) adds up to 34 inches a year; June is the wettest month and January the driest. Rain or snow falls on about 116 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Crystal Lake
93% 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 Forest City 2 Nne, IA.
Living with Crystal Lake’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
159 frost-free days in zone 5a. The last frost comes by Apr 30 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 7.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August and September. 0.0 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Crystal Lake from natural hazards, river flooding is the largest share (26%); heat waves, cold waves, winter storms and ice storms together are 28%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Crystal Lake and similar climates
TownRatings has no climate map of the towns around Crystal Lake yet.
Climates most like Crystal Lake’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 |
|---|---|---|---|---|
| Crystal Lake, IA | 7° | 82° | 34" | 44" |
| Saratoga, WI | 7° | 82° | 34" | 48" |
| Plattsburgh, NY | 9° | 81° | 35" | 50" |
| Wyoming, MN | 5° | 82° | 32" | 52" |
| Colchester, VT | 10° | 81° | 38" | 50" |
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 Crystal Lake averaged 0.8° warmer than the 1900s. The biggest change is in December (+2.5°).
A smaller shift than in 90% 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 Crystal Lake compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Crystal Lake’s place among Iowa’s.
Crystal Lake weather by month
Highs, lows and precipitation from NOAA’s grid at Crystal Lake’s center; snow, wet days and snow on the ground from Mason City Muni Airport. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 24° | 7° | 0.8" | 11.3" | 8 | 24 | 5° – 28° |
| February | 28° | 12° | 1.0" | 10.0" | 8 | 22 | 9° – 31° |
| March | 41° | 24° | 1.9" | 7.0" | 9 | 10 | 25° – 48° |
| April | 57° | 35° | 3.6" | 3.0" | 12 | 1 | 35° – 53° |
| May | 69° | 47° | 4.8" | 0.3" | 14 | 0 | 53° – 65° |
| June | 79° | 58° | 5.1" | 0.0" | 12 | 0 | 65° – 73° |
| July | 82° | 61° | 4.3" | 0.0" | 10 | 0 | 65° – 78° |
| August | 79° | 59° | 4.0" | 0.0" | 9 | 0 | 64° – 74° |
| September | 73° | 51° | 3.5" | 0.0" | 9 | 0 | 55° – 67° |
| October | 60° | 38° | 2.5" | 0.4" | 9 | 0 | 42° – 54° |
| November | 43° | 25° | 1.6" | 3.0" | 8 | 4 | 24° – 47° |
| December | 29° | 14° | 1.2" | 9.4" | 8 | 16 | 6° – 29° |
| Year | 55° | 36° | 34.3" | 44.4" | 116 | 79 |
How much a month can swing
A normal is an average. March swings the most: from 1991 to 2020 its average ranged from 25° to 48°. June is the most reliable, staying within 8°.
Where Crystal Lake’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 Crystal Lake’s center.
- Snow: Mason City Muni Airport.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Forest City 2 Nne, IA, 9 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 Crystal Lake’s climate
What is the weather like in Crystal Lake?
A typical July afternoon reaches 82°, a January night drops to 7°, and about 44 inches of snow falls in a normal winter. Colder January nights than 96% of U.S. towns; cooler July afternoons than 83% of U.S. towns.
How cold does it get in Crystal Lake in winter?
January nights average 7°. About 159 nights a year reach 32° or below and 27 reach 0° or below. In the coldest January of the last 30 years the month averaged 5°.
How much snow does Crystal Lake get?
About 44 inches in a normal winter at Mason City Muni Airport, most of it in January, with snow on the ground about 79 days a year.
How hot does it get in Crystal Lake?
July, with a typical high of 82° and a low of 61°. About 9 days a year reach 90° (Forest City 2 Nne, IA).
When is the first and last frost in Crystal Lake?
In half of years the last spring frost (32°) comes by April 30 and the first fall frost by October 7, about 159 frost-free days, at Forest City 2 Nne, IA.
What growing zone is Crystal Lake in?
Zone 5a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about −19°.
What is the best time of year to visit Crystal Lake?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Crystal Lake getting warmer?
Yes: 1991–2020 averaged 0.8° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 90% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Crystal Lake.
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.