The Spring Equinox: How Much Sun Does Your City Get? | This Month™ Instant Guide

This Month™ · Instant Guide · Spring Science

How Much Sun Does
Your City Get?

On the spring equinox, something remarkable happens — cities from Miami to Seattle all get nearly the same amount of daylight. What changed since winter? What will change by summer?

🌍 Spring Equinox · March 20  |  🔬 Evidence-Based Inquiry
Show me:

☀️ Today, Day and Night Are Almost Equal!

On the spring equinox, the sun shines for about 12 hours in cities all across America. That means day and night are almost the same size! Let’s look at different cities and see how much sunshine they get.

1

Explore Daylight by City Evidence Source

Pick a city. See how many hours of sunshine it gets!

🎯 Teacher tip: Pick a city below together as a class. Click Spring 🌸 to see today’s season!

🌴
Miami
Florida
🍑
Atlanta
Georgia
💻
San Jose
California
🌽
Des Moines
Iowa
🚗
Detroit
Michigan
☕
Seattle
Washington
2

Where Is Your City? Evidence Source

Cities in the north and south get different amounts of sunshine!

🗺️ This map shows where each city is from south to north. Cities near the top are farther from the equator — they get very different amounts of sunshine in summer and winter!

💬
Talk about it: Which city is farthest north? Which city is farthest south? Point to Atlanta on the list. Where is it?
3

Compare Two Cities Evidence Source

Is daylight the same in every city today? Let’s check!

🤔
Look and think: Are the sunny bars the same size? Are they almost the same? What’s different about the two cities?

🎯 What did we notice?

On the spring equinox, all cities get close to 12 hours of daylight — no matter if they are in the north or south. That’s what makes the equinox special!

🔍 A Day That’s Almost Perfectly Split

On the spring equinox, cities from Florida to Washington all get close to 12 hours of daylight. But in winter, some cities get much less sun than others. Where you live on the map changes how your daylight changes through the year.

1

Look Up Daylight Data Evidence Source 1 · City Selector

Choose two cities and compare their daylight across seasons.

Choose two different cities below. For each one, find how many hours of daylight on the Spring equinox (March 20) and on the Winter solstice (December 21).

City #1
City #2
2

The Latitude Connection Evidence Source 2 · Map

Latitude tells us how far north or south a city is. It changes how much daylight shifts through the year.

🌐
Latitude is measured in degrees (°). Cities closer to the equator have low latitude numbers. Cities farther north have high latitude numbers.
🌞
LOW latitude cities
Daylight doesn’t change much from season to season
📊
HIGH latitude cities
Daylight changes a lot — very short winters, very long summers
3

Find the Difference Evidence Source 3 · Calculation

Use the data you found to figure out how much daylight has changed since winter.

For your two cities, subtract the winter hours from the spring hours. How many hours did each city GAIN since December?

🧮 Subtraction equation:

Spring hours  −  Winter hours  =  Hours gained

Example: Atlanta spring (12 hrs) − Atlanta winter (9 hrs 54 min) = about 2 more hours of daylight!

📌 Georgia Math: 2.NR.2.1 / 3.NR.2.1 — Fluently add and subtract within 1,000 to solve practical, mathematical problems

I compared           and          .
In winter,           gets more daylight because it is          .
From winter to spring,           gained    hours of daylight.
Both cities get about    hours of daylight today because it is the equinox.
✏️
Write or say your answer: Which city changed more from winter to spring — the northern one or the southern one? Why do you think that is?

📐 Analyzing the Equinox: A Multi-City Investigation

Today, every city on Earth receives almost exactly 12 hours of daylight. But why does Seattle’s daylight change by over 7 hours between seasons while Miami’s barely shifts 3 hours? Gather evidence from three sources and build your explanation.

1

Collect Daylight Data Evidence Source 1 · City Selector

Use the city selector to record precise sunrise, sunset, and total daylight for two cities across seasons.

Choose two cities below — try to pick one farther south and one farther north for the best comparison. Use the dropdowns to populate your data table.

City Winter Daylight (Dec 21) Spring Daylight (Mar 20) Summer Daylight (Jun 21) Latitude (°N)
— choose below — Record here Record here Record here Record here
— choose below — Record here Record here Record here Record here
2

The Latitude Map Evidence Source 2 · Geography

Compare each city’s position on the map to its daylight data. Look for a pattern.

Each city is plotted at its actual latitude. Summer daylight hours are shown. Notice how the hours increase as you go north.

🌐
Key term: Latitude is the angle between a city and the equator (0°). The equator always gets ~12 hours of daylight. Higher latitudes tilt more dramatically toward or away from the sun as Earth orbits — causing larger seasonal swings.
3

Calculate the Change Evidence Source 3 · Math

Use your data table to complete four calculations for each city.

Select both cities above to unlock the math workspace.

📐 How to complete each calculation

A
Hours gained since winter: Spring daylight − Winter daylight
Example: 12.13 − 9.90 = 2.23 hours gained
📌 Georgia Math: 4.NR.2.1 · 5.NR.4.4 — Subtract decimal numbers to solve practical problems
B
Convert to hours & minutes: Take the decimal part × 60
Example: 2.23 hrs → 2 hours and 0.23 × 60 = 13.8 ≈ 14 minutes
📌 Georgia Math: 4.MDR.6.1 · 5.MDR.7.1 — Convert and solve problems involving time and measurement
C
Minutes gained per day since Dec 21: (Hours gained × 60) ÷ 89 days
Example: 2.23 × 60 = 133.8 min ÷ 89 days ≈ 1.5 min more per day
📌 Georgia Math: 4.NR.2 · 5.MDR.7.1 — Multiply and divide to solve multi-step real-life measurement problems
D
Percent change from winter to spring: ((Spring − Winter) ÷ Winter) × 100
Example: ((12.13 − 9.90) ÷ 9.90) × 100 ≈ 22.5% more daylight
📌 Georgia Math: 5.NR.4.4 · 5.NR.5.1 — Subtract and divide decimals; write and evaluate numerical expressions
City A: Hours gained (Winter→Spring) B: In hours & minutes C: Avg. min gained per day D: % change
City 1 — — — —
City 2 — — — —
4

Analyze Your Evidence

Use data from all three sources to write your explanations.

1
Which of your two cities gained more daylight hours from winter to spring? Using the latitude map (Source 2) as evidence, explain why you think that city changed more.
💡 Hint: Look at the latitude numbers. Which city is farther north? How does that connect to bigger seasonal changes?
Standards: 4.MDR.6.2 · 5.MDR.7.2 — Interpret data displays to answer relevant questions  |  SSMGS8 — Draw conclusions from maps
2
On the equinox, both cities get approximately the same amount of daylight (~12 hours). Use the calculator data and the latitude map together to explain why that happens — even though these cities are in very different places on the map.
💡 Hint: Think about the Earth’s tilt. What is different about how the sun shines on Earth during an equinox vs. a solstice?
Standards: 4.T.RA.1.c · 4.T.RA.2 — Integrate evidence from two or more credible sources  |  SSMGS11 — Compare map with data set to draw conclusions
3
Using your calculation from Step C — how many minutes of extra daylight does your city gain each day between December and March? Predict: will that number be bigger or smaller between March and June? Explain your reasoning.
💡 Challenge: If you wanted to test your prediction, what data would you need to collect?
Standards: 5.NR.5.1 — Write and evaluate numerical expressions in authentic problems  |  5.MDR.7.1 — Solve multi-step problems involving time and measurement
✏️
Extension: What would happen to these patterns if your city was at the equator (0°)? What if it was at the Arctic Circle (66.5°N)? Use what you know from the data to make a prediction.
5

Why Does the Equinox Work This Way?

Background science to connect your data to Earth’s motion.

🌍

Earth’s Tilt

Earth orbits the sun tilted at 23.5°. In winter, the Northern Hemisphere tilts away from the sun — shorter days. In summer, it tilts toward the sun — longer days.

⚖️

The Equinox Moment

On the equinox, neither hemisphere is tilted toward or away from the sun. The sun shines equally on both halves of Earth — so every city gets close to 12 hours of daylight.

📐

Latitude Amplifies Change

Cities farther from the equator (higher latitude) experience a bigger arc of Earth’s tilt — so their seasonal daylight swings are much larger than cities near the equator.

🔁

The Pattern Reverses

After the summer solstice (June 21), the process reverses. Days shorten again. By the fall equinox (September 22), we’re back to equal day and night — and the cycle continues.

📋 Standards Alignment

  • K–1
    K.T.RA.2 / 1.T.RA.2 — Curating Sources & Evidence: Reference parts of texts to address a specific topic or question and explore various sources of information to make connections across a broad range of topics.
  • 2–3
    2.T.RA.2 / 3.T.RA.2 — Curating Sources & Evidence: Integrate evidence from print and digital sources, assessing credibility and relevance and avoiding plagiarism.
  • 3
    3.T.T.2.c — Integrate and explain information from two texts on the same topic in relationship to important points and key details.
  • 4–5
    4.T.RA.1.c / 4.T.RA.2 — Consider and integrate information from research, including relevant and accurate evidence from two or more credible sources.
  • 4–5
    4.T.T.2.c / 5.T.T.2.a — Integrate and classify information from multiple texts on the same topic in relationship to important points and key details; evaluate expository techniques including facts and key details supporting the main idea.
  • K–5
    SSMGS8 — Draw conclusions and make generalizations based on information from maps.
  • K–5
    SSMGS9 — Use latitude and longitude to determine location.
  • 3–5
    SSMGS11 — Compare maps with data sets (charts, tables, graphs) and/or readings to draw conclusions and make generalizations.
  • K–1
    K.MDR.7.3 / 1.MDR.6.4 — Ask questions and answer them based on gathered information, observations, and appropriate graphical displays to solve problems relevant to everyday life. Applied when students observe the day/night split bar and compare “more” or “less” daylight between cities.
  • 2–3
    2.NR.2.1 / 3.NR.2.1 — Fluently add and subtract within 1,000 to solve practical, mathematical problems using place value understanding and properties of operations. Applied in the hours-gained subtraction task: Spring hours − Winter hours = hours gained.
  • 2–3
    2.MDR.5 / 3.MDR.6 — Analyze graphical displays of data to answer relevant questions. Applied when students compare the winter, spring, and summer daylight bars side-by-side for two cities and identify which changed more.
  • 4
    4.NR.2.1 — Fluently add and subtract multi-digit numbers to solve practical, mathematical problems using place value understanding. Applied in Step A: subtracting decimal daylight values (e.g., 12.13 − 9.90) to find hours gained since winter.
  • 4
    4.NR.5.2 / 4.NR.5.3 — Represent and compare decimal numbers as tenths and hundredths using part-whole strategies and visual models. Applied throughout the data table where daylight values are recorded and compared as decimal numbers (e.g., 12.13 hrs, 9.90 hrs).
  • 4
    4.MDR.6.1 — Solve word problems involving elapsed time and metric measurement. Applied in Step B (convert decimal hours to hours and minutes: 0.23 hrs × 60 = 13.8 min) and Step C (total minutes gained ÷ 89 days = avg. minutes gained per day).
  • 4–5
    4.MDR.6.2 / 5.MDR.7.2 — Ask and answer questions based on gathered information and interpret graphical displays of data to answer relevant questions. Applied across all three evidence sources: reading the calculator output, interpreting the latitude bar chart, and drawing conclusions in the analysis questions.
  • 5
    5.NR.4.4 — Add and subtract decimal numbers to the hundredths place to solve relevant, mathematical problems. Applied in Step A (decimal subtraction of daylight hours) and Step D (percent change formula requires decimal subtraction and division).
  • 5
    5.MDR.7.1 — Solve problems involving customary measurements, metric measurements, and time. Applied in Step B (converting hours to minutes: multiply decimal hours × 60) and Step C (dividing total minutes by 89 days to find the daily rate of change).
  • 5
    5.NR.5.1 — Write, interpret, and evaluate numerical expressions within authentic problems. Applied in Step D, where students write and evaluate the percent-change expression: ((Spring − Winter) ÷ Winter) × 100.

📅 THIS MONTH™

Part of the Instant Guide Series

Timely, standards-aligned educational activities connecting learning to the calendar. Designed for K–5 classrooms and families.

Solstices & Equinoxes • Moon Phases • More Instant Guides • thence.us

Activity Description: On the spring equinox, every city in America gets nearly the same amount of daylight — but why does that change so dramatically by summer? This interactive, standards-aligned lesson guides students in grades K–5 through three evidence sources: a geographic map, a latitude pin visualization, and a hands-on data workspace where they compare sunrise and sunset times across six U.S. cities. Students make mathematical calculations, identify patterns between latitude and seasonal daylight change, and build written explanations grounded in real data — all in a single self-navigating guide differentiated for three grade bands.