Lake Breezes and a Long Growing Season

Use school weather data to explain why one shore of a big lake is milder.

A sunny day in May

Read the passage and Table 1. Then answer questions 1–4.

Two Schools, One Lake

1Pine Shoal is a town on the eastern shore of Lake Michigan, with the lake to its west. The town, its neighbors and their numbers are made up, but they are based on real towns around the lake. Cherry and apple orchards cover the low hills near the shore. The weather club at Pine Shoal Middle School runs a station on the school roof, 1 km from the lake. Through a forecast app, club members Rosalind Okafor and Bao Tran share data with a partner school in Cedar Junction, 40 km inland to the east.

2Their science teacher, Mr. Callum Ostrowski, explained that land and water heat up differently. On a sunny day, the ground warms quickly, and so does the air just above it. The lake warms far more slowly, because the sunlight's energy is spread through deep water that keeps mixing, and water takes a lot of energy to warm. At night and in the fall, the land cools quickly, while the lake stays warm much longer. Air that is warmed from below becomes less dense and tends to rise.

3Mr. Ostrowski also described the winds. Pine Shoal is at about 43° north latitude. Near the ground, air moving from the warm tropics toward the North Pole is turned toward the east by Earth's rotation, so at this latitude the winds most often blow from the west. These westerly winds usually cross about 100 km of open lake before they reach Pine Shoal.

4Fruit growers watch the frost dates closely. A frost in spring can kill the blossoms on fruit trees, and the first frost in fall ends the growing season. The club compared long-term records for Pine Shoal, for Cedar Junction, and for Lakeport, a town on the western shore of the lake at the same latitude, with the lake to its east.

Table 1. A Sunny Day in May (lake surface 9 °C)
Time	Pine Shoal (°C)	Pine Shoal wind from	Cedar Junction (°C)	Cedar Junction wind from
9 a.m.	13	Southeast	14	Southeast
11 a.m.	16	South	19	South
1 p.m.	12	West	22	South
3 p.m.	11	West	24	Southwest
5 p.m.	11	West	23	Southwest
9 p.m.	10	Southeast	15	Southeast

At 3 p.m., Cedar Junction was °C warmer than Pine Shoal.

Between which two readings did the wind at Pine Shoal start blowing in from over the lake?

A. 11 a.m. and 1 p.m.
B. 9 a.m. and 11 a.m.
C. 5 p.m. and 9 p.m.
D. 3 p.m. and 5 p.m.

Use paragraph 2. What best explains the wind and temperature at Pine Shoal in the afternoon?

A. Earth's rotation turned the wind around at midday, so the lake air reached the shore after noon.
B. The lake warmed faster than the land in the morning, so warm lake air pushed onto the shore.
C. Sunlight pushed the cool air off the lake, since the morning sun shone from the east.
D. The land warmed faster than the lake, the warm air over land rose, and cool lake air flowed in.

On another May day, the sky is cloudy and drizzly, and Cedar Junction reaches only 12 °C. The lake surface is still 9 °C. What would most likely happen at Pine Shoal that afternoon?

A. A stronger lake breeze than on the sunny day, since the clouds keep the lake cool
B. A sudden warm wind from the lake, since clouds trap the lake's heat
C. A weak lake breeze or none, since the land would warm only a little
D. Wind from the lake by 9 a.m., since the lake is still colder than the land

Lake and land through the year

Use paragraphs 2–4, Table 2 and Table 3 to answer questions 5–11.

Table 2. Monthly Averages (inland air = Cedar Junction)
Month	Lake surface (°C)	Inland air (°C)
February	2	−5
May	9	14
August	22	21
November	9	3

In November, the lake surface is °C warmer than the air at Cedar Junction. In May, it is °C cooler.

Which statement best describes Table 2?

A. The lake changes by more degrees from February to August than the inland air.
B. The lake is cooler than the inland air in spring and warmer in fall.
C. The lake is warmer than the inland air in February, May and August.
D. The lake and the inland air are within 2 °C of each other in each month.

Table 3. Long-Term Averages, Three Towns at About 43°N
Town	January avg. (°C)	July avg. (°C)	Last spring frost	First fall frost	Frost-free days
Lakeport (west shore)	−7	21	May 8	Oct. 5	150
Pine Shoal (east shore)	−4	21	May 5	Oct. 20	168
Cedar Junction (40 km inland)	−6	22	May 12	Oct. 1	142

Pine Shoal has more frost-free days each year than Cedar Junction.

Underline each fact from Table 3 that is evidence that the lake makes Pine Shoal's winters and falls milder.

Pine Shoal averages −4 °C in January, while Lakeport averages −7 °C.Pine Shoal and Lakeport both average 21 °C in July.Pine Shoal's first fall frost comes on October 20, almost three weeks after Cedar Junction's.Cedar Junction averages 22 °C in July, the warmest of the three towns.Pine Shoal's first fall frost comes 15 days after Lakeport's.

Lakeport is on the shore of the same lake and at the same latitude as Pine Shoal. Why are Lakeport's winters and falls colder?

A. The westerly winds push the lake's warm water away from Pine Shoal toward Lakeport.
B. Lakeport is farther from the equator, so its winter sunlight is weaker.
C. The winds usually blow from the west, so Lakeport mostly gets air that crossed land.
D. The lake water is warmer on its eastern side because the Sun sets in the west.

10.

Suppose a large lake lies at about 15° north latitude, where the winds near the ground usually blow from the east. Based on the passage, which shore of that lake would most likely have the mildest climate?

A. The east shore, because the winds start there
B. The west shore, because the winds reach it after crossing the lake
C. The south shore, because it is closer to the equator
D. The north shore, because it is farther from the equator

11.

A grower wants to plant a cherry variety that needs at least 160 frost-free days. Based on Table 3, where should she plant it?

A. Pine Shoal, because it is the only town with more than 160 days
B. Lakeport, because it is also on the shore of the lake
C. Lakeport or Cedar Junction, because both have mild Januaries
D. Cedar Junction, because it has the warmest July of the three

12.

Bao says, "Every town on the shore of Lake Michigan should have the same long growing season, because they are all next to the same lake." Do you agree? Write a claim, give at least two pieces of evidence from Tables 2 and 3, and explain your reasoning using uneven heating of land and water and the winds caused by Earth's rotation.