highest era by a team in a month min 300 games

The Colorado Rockies have the worst ERA by a team when pitching in 300+ games, with an ERA of 5.21 in Junes.

	TEAM	ERA	G	MONTH	W%	W	L	SO	SHO	SV	IP	H	ER	R	HR	BB	HBP	IBB	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Rockies	5.21	871	June	.463	403	468	5,702	6	194	7716.1	8,618	4,468	4,822	1,082	2,993	358	258	34,237	347	6.65	3.49	1.91	1.26	16.7	8.7	1.50	.313	5.62	10.05
2	Rockies	5.08	837	September	.477	399	438	5,751	6	198	7438.2	8,136	4,196	4,523	1,048	3,026	362	200	32,955	336	6.96	3.66	1.90	1.27	17.5	9.2	1.50	.311	5.47	9.84
3	Rockies	5.08	838	July	.447	375	463	5,402	4	195	7367.0	8,104	4,155	4,439	1,016	2,826	294	221	32,451	278	6.60	3.45	1.91	1.24	16.6	8.7	1.48	.309	5.42	9.90
4	Rockies	5.00	760	April	.461	350	410	5,012	6	182	6750.0	7,239	3,752	4,107	833	2,869	286	192	29,888	288	6.68	3.83	1.75	1.11	16.8	9.6	1.50	.307	5.48	9.65
5	Rockies	4.98	916	August	.454	416	500	6,058	6	197	8082.1	8,735	4,472	4,802	1,131	3,119	336	241	35,441	330	6.75	3.47	1.94	1.26	17.1	8.8	1.47	.307	5.35	9.73
6	Rockies	4.93	893	May	.442	395	498	5,859	6	192	7865.0	8,427	4,305	4,634	939	3,175	305	222	34,554	342	6.70	3.63	1.85	1.07	17.0	9.2	1.48	.308	5.30	9.64
7	Marlins	4.53	909	August	.432	393	516	6,603	10	217	8044.1	8,179	4,046	4,392	1,003	3,238	336	287	35,050	294	7.39	3.62	2.04	1.12	18.8	9.2	1.42	.301	4.91	9.15
8	Marlins	4.44	857	September	.464	398	459	6,235	11	202	7608.1	7,612	3,753	4,074	889	3,135	314	257	33,145	293	7.38	3.71	1.99	1.05	18.8	9.5	1.41	.298	4.82	9.00
9	Mariners	4.43	1,351	August	.465	628	723	8,887	21	338	12039.1	12,235	5,922	6,490	1,521	4,442	417	328	52,007	434	6.64	3.32	2.00	1.14	17.1	8.5	1.39	.292	4.85	9.15
10	Diamondbacks	4.43	724	June	.486	352	372	5,429	4	160	6452.0	6,568	3,173	3,497	840	2,270	276	167	27,881	256	7.57	3.17	2.39	1.17	19.5	8.1	1.37	.300	4.88	9.16
11	Royals	4.42	1,497	July	.476	713	784	8,748	37	350	13296.1	13,887	6,534	7,182	1,499	4,842	467	347	57,680	536	5.92	3.28	1.81	1.01	15.2	8.4	1.41	.294	4.86	9.40
12	Rangers	4.42	1,714	July	.459	786	927	10,196	46	366	15215.2	15,445	7,470	8,224	1,776	5,888	537	430	65,899	531	6.03	3.48	1.73	1.05	15.5	8.9	1.40	.288	4.86	9.14
13	Mariners	4.41	1,320	May	.473	625	695	8,528	24	291	11746.0	11,766	5,750	6,280	1,432	4,576	381	306	50,644	429	6.53	3.51	1.86	1.10	16.8	9.0	1.39	.289	4.81	9.02
14	Rays	4.37	699	July	.469	328	371	5,229	9	196	6187.2	6,102	3,005	3,242	781	2,219	253	115	26,556	239	7.61	3.23	2.36	1.14	19.7	8.4	1.34	.294	4.72	8.88
15	Blue Jays	4.36	1,106	April	.486	537	568	7,324	17	259	9866.1	9,728	4,776	5,223	1,161	3,903	376	236	42,538	344	6.68	3.56	1.88	1.06	17.2	9.2	1.38	.288	4.76	8.87
16	Rays	4.35	664	April	.482	320	344	4,754	8	150	5901.0	5,657	2,855	3,116	724	2,267	290	120	25,309	247	7.25	3.46	2.10	1.10	18.8	9.0	1.34	.286	4.75	8.63
17	Mariners	4.35	1,239	July	.468	580	659	8,247	33	292	11082.1	11,096	5,353	5,849	1,377	3,877	416	299	47,534	418	6.70	3.15	2.13	1.12	17.3	8.2	1.35	.289	4.75	9.01
18	Diamondbacks	4.34	731	September	.469	343	388	5,590	8	176	6509.1	6,350	3,141	3,400	852	2,393	241	168	27,919	225	7.73	3.31	2.34	1.18	20.0	8.6	1.34	.292	4.70	8.78
19	Mariners	4.32	1,127	April	.485	546	580	7,441	14	282	10020.0	9,955	4,813	5,288	1,162	3,953	417	240	43,331	404	6.68	3.55	1.88	1.04	17.2	9.1	1.39	.290	4.75	8.94
20	Royals	4.31	1,535	May	.466	715	818	9,089	33	332	13708.2	13,975	6,560	7,130	1,520	5,052	419	325	59,083	541	5.97	3.32	1.80	1.00	15.4	8.6	1.39	.290	4.68	9.17
21	Rangers	4.30	1,779	May	.487	865	913	10,448	42	417	15826.0	16,035	7,566	8,462	1,730	6,194	488	426	68,533	565	5.94	3.52	1.69	0.98	15.2	9.0	1.40	.288	4.81	9.12
22	Diamondbacks	4.28	784	August	.508	398	386	5,990	12	198	7011.0	7,032	3,336	3,624	879	2,427	273	216	30,098	285	7.69	3.12	2.47	1.13	19.9	8.1	1.35	.300	4.65	9.03
23	Blue Jays	4.28	1,239	July	.498	617	622	8,195	27	293	11076.1	11,195	5,266	5,710	1,287	3,972	387	264	47,550	398	6.66	3.23	2.06	1.05	17.2	8.4	1.37	.294	4.64	9.10
24	Rays	4.28	743	September	.467	347	396	5,800	5	183	6590.0	6,312	3,133	3,405	845	2,417	261	128	28,161	287	7.92	3.30	2.40	1.15	20.6	8.6	1.32	.290	4.65	8.62
25	Blue Jays	4.27	1,369	August	.496	678	690	8,785	23	338	12207.2	12,260	5,798	6,369	1,463	4,460	466	293	52,460	417	6.48	3.29	1.97	1.08	16.7	8.5	1.37	.290	4.70	9.04