Summer frost, snow and hail days

Days in lunar months 5–7 recording frost, snow or hail, per 1,000 articles classified 'science–weather' in the same decade.

×1.3frost+snow rate 1640–1719 vs 1500–1639

Key point

Tested against the Sillok, the Little Ice Age hypothesis is supported for 1640–1719 rather than across 1500–1750. Because keyword precision is only 54%, use the series for comparisons between decades, not as absolute counts.

Formula: Record days / weather-class articles × 1,000, by decade
How to read it: Frost and snow reports rise in 1640–1719, while the whole 1500–1750 span is not elevated. The table is a national total; no regional breakdown is published here.
Caveats: The solar term '霜降' and figurative uses were removed by sample coding; precision is on the card. This is the frequency of anomaly reports, not climate.

Reliability card: sampledSampled precision — share of keyword hits that mean what the metric says, measured on a coded stratified sample
Precision 54.4% (Wilson 95% 43.5%–65.0%) on a coded stratified sample of 79 articles (10 per 50-year period, principal editions). One article left undecided was counted as 'no'. The codebook and all judgments can be downloaded from the Data page.

By decade, record days per 1,000 weather-class articles; decades with fewer than 100 such articles (most after the 1780s) are omitted. Band: 1640–1719.

Decade	Weather-class articles	Frost days	Snow days	Hail days	Frost+snow/1,000	Hail/1,000	Plotted
1390	367	3	3	4	16.3	10.9	True
1400	702	7	6	15	18.5	21.4	True
1410	744	15	8	14	30.9	18.8	True
1420	634	5	9	2	22.1	3.2	True
1430	631	4	21	8	39.6	12.7	True
1440	399	4	10	7	35.1	17.5	True
1450	573	3	14	0	29.7	0.0	True
1460	337	1	10	0	32.6	0.0	True
1470	617	7	21	6	45.4	9.7	True
1480	460	2	13	13	32.6	28.3	True
1490	662	9	26	17	52.9	25.7	True
1500	672	4	13	27	25.3	40.2	True
1510	1,150	6	10	48	13.9	41.7	True
1520	1,510	17	19	96	23.8	63.6	True
1530	1,750	10	9	22	10.9	12.6	True
1540	1,437	19	18	41	25.7	28.5	True
1550	2,029	7	11	28	8.9	13.8	True
1560	1,241	3	5	19	6.4	15.3	True
1570	74	2	11	3	175.7	40.5	False
1580	94	1	5	2	63.8	21.3	False
1590	626	13	20	10	52.7	16.0	True
1600	839	14	24	18	45.3	21.5	True
1610	345	3	17	6	58.0	17.4	True
1620	664	2	6	19	12.0	28.6	True
1630	611	7	2	11	14.7	18.0	True
1640	994	24	14	26	38.2	26.2	True
1650	1,012	12	14	23	25.7	22.7	True
1660	951	5	4	17	9.5	17.9	True
1670	815	10	14	38	29.4	46.6	True
1680	979	4	10	7	14.3	7.2	True
1690	554	10	10	19	36.1	34.3	True
1700	677	11	11	17	32.5	25.1	True
1710	687	9	9	25	26.2	36.4	True
1720	483	3	16	14	39.3	29.0	True
1730	655	7	17	15	36.6	22.9	True
1740	547	6	12	16	32.9	29.3	True
1750	344	4	7	4	32.0	11.6	True
1760	486	3	3	6	12.3	12.3	True
1770	239	2	9	2	46.0	8.4	True
1780	111	5	7	2	108.1	18.0	True
1790	69	15	13	0	405.8	0.0	False
1800	100	8	8	6	160.0	60.0	True
1810	76	1	1	1	26.3	13.2	False
1820	14	2	1	1	214.3	71.4	False
1830	33	1	0	1	30.3	30.3	False
1840	7	0	0	0	0.0	0.0	False
1850	1	1	1	0	2000.0	0.0	False

Download CSV: c_weather.csv