diff --git a/tests/testClimate.cpp b/tests/testClimate.cpp
new file mode 100644
index 0000000..f5498aa
--- /dev/null
+++ b/tests/testClimate.cpp
@@ -0,0 +1,214 @@
+#include "testHarness.h"
+#include "vf/Climate.h"
+#include "vf/BiomeGen.h"
+
+using namespace vf;
+
+namespace {
+
+ClimateConfig coldConfig() {
+    ClimateConfig cfg;
+    cfg.freezeTemperature = 100.0f;
+    cfg.meltTemperature = 200.0f;
+    return cfg;
+}
+
+ClimateConfig warmConfig() {
+    ClimateConfig cfg;
+    cfg.freezeTemperature = -100.0f;
+    cfg.meltTemperature = -100.0f;
+    return cfg;
+}
+
+ClimateConfig neutralConfig() {
+    ClimateConfig cfg;
+    cfg.freezeTemperature = -100.0f;
+    cfg.meltTemperature = 200.0f;
+    return cfg;
+}
+
+} // namespace
+
+VF_TEST(temperatureFallsWithHeightAndLatitude) {
+    BiomeGen biomes;
+    Climate climate(biomes);
+    float atSea = climate.temperatureAt(50, climate.settings().seaLevel, 0);
+    float aloft = climate.temperatureAt(50, climate.settings().seaLevel + 80, 0);
+    float polar = climate.temperatureAt(50, climate.settings().seaLevel, 4000);
+    CHECK(aloft < atSea);
+    CHECK(polar < atSea);
+}
+
+VF_TEST(exposedWaterFreezesWhenColdButCoveredWaterDoesNot) {
+    BiomeGen biomes;
+    Climate climate(biomes, coldConfig());
+    World world;
+    world.setBlock(10, 30, 10, Block::Water);
+    world.setBlock(14, 30, 10, Block::Water);
+    world.setBlock(14, 31, 10, Block::Stone);
+
+    std::vector<ClimateChange> changes = climate.tick(world, Vec3i{8, 30, 8}, Vec3i{10, 4, 6},
+                                                    Precipitation::None);
+    Climate::apply(world, changes);
+
+    CHECK(world.blockAt(10, 30, 10) == Block::Ice);
+    CHECK(world.blockAt(14, 30, 10) == Block::Water);
+}
+
+VF_TEST(iceThawsWhenWarm) {
+    BiomeGen biomes;
+    Climate climate(biomes, warmConfig());
+    World world;
+    world.setBlock(5, 40, 5, Block::Ice);
+
+    std::vector<ClimateChange> changes = climate.tick(world, Vec3i{4, 40, 4}, Vec3i{4, 2, 4},
+                                                    Precipitation::None);
+    Climate::apply(world, changes);
+    CHECK(world.blockAt(5, 40, 5) == Block::Water);
+}
+
+VF_TEST(iceMeltsBesideHeatSourceOnlyWhenAdjacent) {
+    BiomeGen biomes;
+    Climate climate(biomes, neutralConfig());
+    World world;
+    world.setBlock(20, 50, 20, Block::Ice);
+    world.setBlock(21, 50, 20, Block::Lava);
+    world.setBlock(25, 50, 20, Block::Ice);
+
+    std::vector<ClimateChange> changes = climate.tick(world, Vec3i{18, 49, 18}, Vec3i{12, 4, 6},
+                                                    Precipitation::None);
+    Climate::apply(world, changes);
+    CHECK(world.blockAt(20, 50, 20) == Block::Water);
+    CHECK(world.blockAt(25, 50, 20) == Block::Ice);
+}
+
+VF_TEST(snowAccumulatesUnderSnowfallAndStopsWithoutIt) {
+    BiomeGen biomes;
+    Climate climate(biomes, coldConfig());
+    World world;
+    world.setBlock(0, 30, 0, Block::Stone);
+    Vec3i origin{-1, 30, -1};
+    Vec3i dims{3, 5, 3};
+    Vec3i snowCell{0, 31, 0};
+
+    std::vector<ClimateChange> first = climate.tick(world, origin, dims, Precipitation::Snow);
+    Climate::apply(world, first);
+    CHECK(world.blockAt(0, 31, 0) == Block::SnowLayer);
+    CHECK_EQ(climate.snowDepthAt(snowCell), 1);
+
+    for (int i = 0; i < 3; ++i) {
+        std::vector<ClimateChange> more = climate.tick(world, origin, dims, Precipitation::Snow);
+        Climate::apply(world, more);
+    }
+    CHECK_EQ(climate.snowDepthAt(snowCell), 4);
+
+    int depthBefore = climate.snowDepthAt(snowCell);
+    std::vector<ClimateChange> dry = climate.tick(world, origin, dims, Precipitation::None);
+    Climate::apply(world, dry);
+    CHECK_EQ(climate.snowDepthAt(snowCell), depthBefore);
+}
+
+VF_TEST(snowDepthClampsAtMax) {
+    BiomeGen biomes;
+    ClimateConfig cfg = coldConfig();
+    cfg.maxSnowDepth = 3;
+    Climate climate(biomes, cfg);
+    World world;
+    world.setBlock(0, 30, 0, Block::Stone);
+    Vec3i origin{-1, 30, -1};
+    Vec3i dims{3, 5, 3};
+
+    for (int i = 0; i < 10; ++i) {
+        std::vector<ClimateChange> changes = climate.tick(world, origin, dims, Precipitation::Snow);
+        Climate::apply(world, changes);
+    }
+    CHECK_EQ(climate.snowDepthAt(Vec3i{0, 31, 0}), 3);
+}
+
+VF_TEST(iceCompactsToPackedIceInProlongedCold) {
+    BiomeGen biomes;
+    ClimateConfig cfg = coldConfig();
+    cfg.packThreshold = 4;
+    Climate climate(biomes, cfg);
+    World world;
+    world.setBlock(5, 40, 5, Block::Ice);
+    Vec3i origin{4, 40, 4};
+    Vec3i dims{4, 3, 4};
+
+    for (int i = 0; i < 3; ++i) {
+        std::vector<ClimateChange> changes = climate.tick(world, origin, dims, Precipitation::None);
+        Climate::apply(world, changes);
+    }
+    CHECK(world.blockAt(5, 40, 5) == Block::Ice);
+    CHECK_EQ(climate.iceAgeAt(Vec3i{5, 40, 5}), 3);
+
+    std::vector<ClimateChange> last = climate.tick(world, origin, dims, Precipitation::None);
+    Climate::apply(world, last);
+    CHECK(world.blockAt(5, 40, 5) == Block::PackedIce);
+}
+
+VF_TEST(frostSpreadsFromExistingIceButNotAcrossOpenWater) {
+    BiomeGen biomes;
+    ClimateConfig cfg;
+    cfg.freezeTemperature = -100.0f;
+    cfg.frostSpreadTemperature = 100.0f;
+    cfg.meltTemperature = 200.0f;
+    Climate climate(biomes, cfg);
+    World world;
+    world.setBlock(10, 40, 10, Block::Ice);
+    world.setBlock(11, 40, 10, Block::Water);
+    world.setBlock(20, 40, 10, Block::Water);
+
+    std::vector<ClimateChange> changes = climate.tick(world, Vec3i{8, 40, 8}, Vec3i{16, 3, 6},
+                                                    Precipitation::None);
+    Climate::apply(world, changes);
+    CHECK(world.blockAt(11, 40, 10) == Block::Ice);
+    CHECK(world.blockAt(20, 40, 10) == Block::Water);
+}
+
+VF_TEST(packedIceMeltsBesideHeat) {
+    BiomeGen biomes;
+    ClimateConfig cfg = coldConfig();
+    cfg.packThreshold = 2;
+    Climate climate(biomes, cfg);
+    World world;
+    world.setBlock(5, 40, 5, Block::Ice);
+    Vec3i origin{4, 40, 4};
+    Vec3i dims{4, 3, 4};
+
+    for (int i = 0; i < 2; ++i) {
+        std::vector<ClimateChange> changes = climate.tick(world, origin, dims, Precipitation::None);
+        Climate::apply(world, changes);
+    }
+    CHECK(world.blockAt(5, 40, 5) == Block::PackedIce);
+
+    world.setBlock(6, 40, 5, Block::Lava);
+    std::vector<ClimateChange> melt = climate.tick(world, origin, dims, Precipitation::None);
+    Climate::apply(world, melt);
+    CHECK(world.blockAt(5, 40, 5) == Block::Water);
+}
+
+VF_TEST(accumulatedSnowMeltsBesideHeat) {
+    BiomeGen biomes;
+    Climate climate(biomes, coldConfig());
+    World world;
+    world.setBlock(0, 30, 0, Block::Stone);
+    Vec3i origin{-1, 30, -1};
+    Vec3i dims{3, 5, 3};
+    Vec3i snowCell{0, 31, 0};
+
+    for (int i = 0; i < 5; ++i) {
+        std::vector<ClimateChange> changes = climate.tick(world, origin, dims, Precipitation::Snow);
+        Climate::apply(world, changes);
+    }
+    int peak = climate.snowDepthAt(snowCell);
+    CHECK(peak > 1);
+
+    world.setBlock(1, 31, 0, Block::Torch);
+    for (int i = 0; i < peak; ++i) {
+        std::vector<ClimateChange> changes = climate.tick(world, origin, dims, Precipitation::None);
+        Climate::apply(world, changes);
+    }
+    CHECK_EQ(climate.snowDepthAt(snowCell), 0);
+    CHECK(world.blockAt(0, 31, 0) == Block::Air);
+}